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Security Evangelist at Gen

Threat Operations Analyst at Gen

Research

<p>A fake invoice in your email is easy to ignore. A fake invoice inside your order history feels different.&nbsp;</p><p>Norton customers have reported fake Norton invoices appearing inside the Shop app, the shopping and order-tracking app from Shopify. Public reports suggest the same technique is not limited to Norton. Similar suspicious Shop app notifications have used McAfee, Apple gift cards, iPhones, PayPal-style payment claims and other high-value purchases as bait. The impersonated brand may change, but the mechanics are familiar: make the user believe they have been charged, then give them a phone number to call.&nbsp;</p><p>That phone number is where the scam really begins.&nbsp;</p><h4>Why the Shop app makes this more believable&nbsp;</h4><p>Shop is a legitimate app. People use it to track packages, check receipts and receive order updates. According to Shop’s own documentation, the app can automatically track orders from several sources, including Gmail, Outlook, the email address linked to the user’s Shop account and orders paid through Shop Pay. If Gmail or Outlook is connected, Shop says it scans recent emails for keywords such as “tracking number” and “track your package” to populate deliveries in the Orders tab.&nbsp;</p>

<p>Shop also supports push notifications for delivery updates, payments and favorite products. So the first alert the victim sees may not be an email, an SMS or a calendar invite. It may be a notification from an app they already use for real purchases.&nbsp;</p><p>That context matters. The scam text is not especially polished. Some of the examples we reviewed contain awkward wording and obvious signs of fraud. But when the message appears inside an order-tracking app, surrounded by real receipts and shipping updates, users may give it more credibility than it deserves.&nbsp;</p><p>The screenshots reported to us show fake orders under generic seller names such as “My Store.” The receipts claim that a Norton or Norton LifeLock subscription has been activated or renewed, usually for several hundred dollars. The phone number appears in the product description, the receipt body or even the shipping address field.&nbsp;</p><p>That is not how a normal receipt should look.&nbsp;</p><h4>The brand is interchangeable&nbsp;</h4><p>Norton is the example we saw through customer reports. Norton support now warns that scammers may abuse Android and iOS shopping platforms or applications to generate fake order notifications that appear to be legitimate Norton purchases. Those notifications may include fake order confirmations, fake charges, trusted third-party app delivery and fake support phone numbers embedded in order details.&nbsp;</p><p>Public user reports point to a wider pattern. One Reddit user described receiving a Shop.app message about a transaction they did not recognize, with no follow-up email confirmation, and a message telling them to call support if the order was not placed by them. Another thread includes reports of unrecognized iPhone purchases under “My Store,” suspicious contact emails and users saying they saw no matching charges on their bank cards. Other reports mention fictitious Apple gift card purchases and iPhone orders using the same kind of wording: “If Order Not Placed By You,” followed by a phone number.&nbsp;</p><p>The choice of brand is part of the social engineering. A fake security subscription charge plays on two fears at once: being billed for something you did not buy, and being left unprotected if you ignore it. Apple products and gift cards create high-value purchase panic. PayPal-style wording makes users worry about payment account abuse. In each case, the fake order is there to push the victim toward a call.&nbsp;</p><h4>What we know, and what we do not&nbsp;</h4><p>We have not found any evidence that any of the impersonated brands have been compromised.&nbsp;&nbsp;</p><p>We also should not claim that Shop or Shopify was breached based on the evidence we have. The exact abuse path still needs confirmation. The fake order may be entering the app through a merchant/order workflow, through email parsing, through account association, or through another legitimate mechanism that scammers have found a way to misuse. Shop’s own documentation shows that orders can populate from multiple sources, so assuming one route would be premature.&nbsp;&nbsp;</p><p>What we can say is narrower and stronger: scammers are placing fake purchase claims inside shopping app order experiences, where users are used to seeing real receipts and order updates. Norton’s own support page now describes this class of shopping app scam, and public reports show similar lures using other brands and products.&nbsp;&nbsp;</p><p>That is enough to warn users without overstating the technical evidence.&nbsp;</p><h4>How the scam works&nbsp;</h4><p>The user receives a notification or sees a new order in the Shop app. The order looks like a receipt for something expensive: a security subscription, an Apple gift card, an iPhone, a MacBook or another high-value purchase.</p>

<p>The receipt says the charge has been processed, the subscription has renewed, or the order is being prepared. Somewhere in the order details, the scammer inserts a phone number, email address or support instruction.&nbsp;</p><p>The wording is often clumsy. We have seen phrases like “If Order Not Place By You” and “If Need Help.” Those errors may look obvious when reviewing a screenshot. They are easier to miss when a phone notification tells you that hundreds of dollars have just been charged.&nbsp;</p><p>If the victim calls, the scam moves off-platform. The person answering may claim to be billing support, Norton support, PayPal support or a cancellation department. The script can vary, but the request usually moves toward credentials, payment data, one-time codes or remote access software.&nbsp;</p><p>By that point, the fake receipt has done its job. It has created enough urgency for the victim to enter a conversation controlled by the scammer.&nbsp;</p><h4>Why this is harder for users to judge&nbsp;</h4><p>Most people understand that email can be spam. They may still fall for phishing, but at least the inbox is a place where scams are expected.&nbsp;</p><p>Order-tracking apps are different. Their purpose is to collect receipts, shipping updates and purchase information in one place. A notification from that environment can feel as if it has already passed through some layer of trust, even when the content inside the order is fraudulent.&nbsp;</p><p>We have seen the same logic with calendar invite scams. The message itself is not always convincing, but the delivery channel changes how people read it. A fake invoice in an inbox is one thing. A fake invoice inside a calendar reminder or shopping app receipt can feel closer to a real event.&nbsp;</p><p>For security products, this also creates a detection problem. The first visible alert may not be an email, SMS or malicious website. It may be a legitimate app notification carrying fraudulent text. The scam still depends on social engineering, but the delivery surface is harder to classify with the usual rules.&nbsp;</p><h4>What to do if you see one&nbsp;</h4><p>Do not call the number in the receipt.&nbsp;</p><p>Check the charge directly. Open your bank or credit card app. Open the official account for the brand being impersonated. If it claims to be Norton, go to your Norton account or official Norton support. If it claims to involve PayPal, open PayPal directly. Do not use the phone number, email address or link inside the suspicious order.&nbsp;</p><p>If there is no matching charge, treat the receipt as a scam attempt.&nbsp;</p><p>Report the suspicious store or message in the Shop app if the option is available. Shop’s help pages say suspicious Shop stores can be reported from the store page through the app, and Shopify also tells users to forward phishing messages to its phishing inbox.&nbsp;&nbsp;</p><p>Norton users can forward suspicious messages to Norton and should verify unexpected charges only through their Norton account or official Norton support channels.&nbsp;&nbsp;</p><p>Opening the receipt does not automatically mean your device was compromised. The risk increases if you call the number, share information, install software or follow instructions from the person on the phone.&nbsp;</p><h4>What to do if you have already called&nbsp;</h4><p>End the call.&nbsp;</p><p>If you shared payment details, contact your bank or card provider immediately using the number on your card or inside your banking app. If you gave away a password, change it from a different device if possible. Start with your email account, Apple ID or Google account, banking account and any account connected to the fake invoice.&nbsp;</p><p>If you installed remote access software, disconnect the device from the internet and remove the software. Run a security scan before using the device again for banking, email or shopping.&nbsp;</p><p>If you gave a one-time code to the caller, treat the related account as compromised. Change the password, review recovery options and check recent login activity.&nbsp;</p><h4>The lesson&nbsp;</h4><p>Scammers keep testing new places to put old tricks. For years, fake invoices were mostly an email problem. Then similar subscription notices appeared in calendar invites. Now we are seeing fake receipts inside shopping app order histories and push notification flows.&nbsp;</p><p>The safest response is to separate the alert from the action. If an app, email, text message or calendar invite says you have been charged, do not use the contact details inside that alert. Go directly to the account or payment provider yourself. Check whether the charge exists. Use official support channels.&nbsp;</p><p>The fake receipt, the fake support number and the fake emergency are all part of the same controlled environment. The moment you verify the charge somewhere else, the scam loses most of its power.&nbsp;</p>

Scammers are using order-tracking apps to place fake receipts where users expect to see real purchases, then pushing them to call fake support numbers. 

Fake invoices are moving from inboxes to shopping apps 

Threat Researcher at Gen

<h2>Introduction&nbsp;</h2><p>Infostealers are constantly evolving, and so are the techniques they use to bypass <a href="https://security.googleblog.com/2024/07/improving-security-of-chrome-cookies-on.html" target="_blank" rel="noreferrer noopener">Application-Bound Encryption (ABE)</a>. In recent weeks, Vidar has been among the most actively developed stealers and, apart from <a href="https://x.com/GenThreatLabs/status/2064836539952361976" target="_blank" rel="noreferrer noopener">multiple updates to its string obfuscation</a> and <a href="https://x.com/GenThreatLabs/status/2061462524604649840" target="_blank" rel="noreferrer noopener">a reworked approach to protecting its configuration</a>, it has also introduced a novel technique for bypassing ABE. And while there have been many other changes in Vidar lately, with new versions dropping every week, in this blog post we focus solely on the ABE bypass and its technical aspects.&nbsp;<br>&nbsp;</p><h2>The ABE Bypass&nbsp;</h2><p>From a high-level perspective, Vidar’s approach to bypassing ABE is somewhat similar to that of Remus/Lumma, in that both try to extract the <code>v20_master_key</code> directly from the browser’s memory. What sets them apart, however, is how they achieve it. Since we’ve already covered the inner workings of ABE in earlier posts (<a href="https://www.gendigital.com/blog/insights/research/remus-64bit-variant-of-lumma-stealer" target="_blank" rel="noreferrer noopener">Remus</a>, <a href="https://www.gendigital.com/blog/insights/research/voidstealer-abe-bypass" target="_blank" rel="noreferrer noopener">VoidStealer</a>), we don’t revisit them here and focus instead on the bypass itself. For readers interested in the broader background, we encourage checking those earlier posts.&nbsp;&nbsp;</p><p>In short, the end goal of infostealers is to obtain the <code>v20_master_key</code>, as it alone is sufficient for decrypting any ABE-protected data tied to a specific application. This key can be obtained in one of two ways: either from disk, where it is protected by two layers of <code>CryptProtectData</code> (one applied in the context of the logged-in user and one as <code>NT AUTHORITY\SYSTEM</code>), or from the browser’s memory – the direction Vidar took.&nbsp;</p><p>In memory, however, the key is kept protected with <code>CryptProtectMemory</code> using the <code>CRYPTPROTECTMEMORY_SAME_PROCESS</code> flag. This ensures that even if an attacker manages to read the encrypted form of the key from memory, they cannot simply decrypt it (they would need to invoke the complementary <code>CryptUnprotectMemory</code> function directly from within the browser process). That leaves attackers with two problems to solve: how to find the encrypted key in memory, and how to get it decrypted.&nbsp;</p><h2>Locating the v20_master_key in Browser’s Memory&nbsp;</h2><p>Vidar’s approach to locating the encrypted <code>v20_master_key</code> in memory involves scanning the entire memory of a running browser for a specific pattern. But that first requires a browser process to scan.&nbsp;</p><p>When the target browser is already running, Vidar reuses the existing process. However, it doesn’t read its memory directly. Instead, it creates a fork of it using <code>NtCreateProcessEx</code> with <code>SectionHandle</code> set to <code>NULL</code>, instructing the kernel to clone the address space of the process specified by the <code>ParentProcess</code> as a copy-on-write mapping. The resulting process has no threads and is never resumed – it exists purely as a static memory snapshot.&nbsp;&nbsp;</p><p>To perform the fork, Vidar first opens a handle to the target browser via <code>OpenProcess</code> with <code>PROCESS_QUERY_INFORMATION | PROCESS_CREATE_PROCESS | PROCESS_VM_READ</code>, falling back to <code>PROCESS_CREATE_PROCESS</code> if the initial call fails. It then passes this handle as the <code>ParentProcess</code> argument to <code>NtCreateProcessEx</code>, requesting <code>PROCESS_ALL_ACCESS</code> on the resulting child. If the fork fails, Vidar falls back to scanning the live browser process directly.&nbsp;</p>

<p>If no target browser process is found running, Vidar creates a new isolated desktop via <code>CreateDesktopA</code>, assigns it a name of the form <code>v20_%d</code> (where <code>%d</code> is replaced with the browser’s index in Vidar’s configuration), and launches the target browser in there. In the case of Vidar version 2.1, the browser is launched with the command line <code>--no-first-run --disable-gpu about:blank</code>, although the exact command line varies across versions. Since modern browsers use a multi-process architecture, there are typically multiple processes matching a given browser. Vidar enumerates all of them (up to 64) and applies the fork-and-scan procedure to each one independently.&nbsp;</p>

<p>With a handle to the forked process in hand, Vidar proceeds to enumerate its virtual memory regions using <code>NtQueryVirtualMemory</code>. It iterates through the entire browser’s address space, collecting regions that match a specific profile: committed (<code>MEM_COMMIT</code>), private (<code>MEM_PRIVATE</code>), and either readable (<code>PAGE_READONLY</code>) or read-write (<code>PAGE_READWRITE</code>). Vidar records up to 4096 memory regions matching these requirements, along with their base addresses and sizes.<strong> </strong>The actual pattern scanning is then performed in parallel with up to 64 worker threads, depending on the system.&nbsp;&nbsp;</p>

<p>Each thread scans its assigned regions using <code>NtReadVirtualMemory</code>, searching for a 32-byte pattern. When a match is found, the thread reads 8 bytes at offset +32 from the match, interprets them as a pointer, and validates that it points to committed, private, and readable memory (the expected memory state for the encrypted <code>v20_master_key</code>).&nbsp;&nbsp;</p>

<p>This naturally raises the question of what pattern Vidar searches for. The answer is a 32-byte signature: <code>76 32 30 00 ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? 03 00 00 00 00 01 ?? ?? ??</code>, where <code>??</code> denotes a wildcard (Vidar uses the byte <code>AA</code> as the wildcard marker in its internal representation). Notably, the first four bytes correspond to the ASCII <code>v20\x00</code>, which is a common prefix used for ABE-related data.&nbsp;&nbsp;</p>

<p>We assess with high confidence that this pattern is intended to match a node structure within Chromium’s <code>Encryptor::KeyRing</code>, the structure that holds the keys used by the <code>Encryptor</code> class. Now, this part is admittedly a bit tricky as it relies on several assumptions we made about the internal memory layout, as well as on implementation-specific representations of various C++ standard library types <code>(std::map</code>, <code>std::string</code>, <code>std::vector</code>, <code>std::optional</code>), which is why we frame this as a high-confidence rather than a certainty.&nbsp;&nbsp;</p><p>Our reasoning is as follows: <code>KeyRing</code> is <a href="https://github.com/chromium/chromium/blob/cf5d502bcaedb22927e3829a18be1ff6d8b6f598/components/os_crypt/async/common/encryptor.h#L132" target="_blank" rel="noreferrer noopener">defined</a> as <code>std::map&lt;/*tag=*/std::string, std::optional&lt;Key&gt;&gt;</code>, and <code>std::map</code> is typically implemented as a red-black tree, where each tree node stores three pointers (left child, parent, and right child) followed by the key-value pair. In this case, the pair is in the form of <code>std::pair&lt;/*tag=*/std::string, std::optional&lt;Key&gt;&gt;</code>, meaning that the <code>std::string</code> and the <code>Key</code> object might be laid out consecutively in memory within each node. For a <code>v20_master_key</code> entry, the tag corresponds to the string <code>v20</code>, which at 4 bytes including the null terminator fits within the small string optimization (SSO) buffer and is therefore stored inline rather than heap-allocated. The <code>Key</code> class that immediately follows <a href="https://github.com/chromium/chromium/blob/cf5d502bcaedb22927e3829a18be1ff6d8b6f598/components/os_crypt/async/common/encryptor.h#L93-L98" target="_blank" rel="noreferrer noopener">contains three member variables</a>: <code>std::optional&lt;mojom::Algorithm&gt; algorithm_</code>, <code>std::vector&lt;uint8_t&gt; key_</code>, and <code>bool encrypted_ = false</code>.&nbsp;</p><p>Putting it all together and applying it to a concrete example from a browser memory dump, we get the following layout:&nbsp;</p>

<p>Please note that while the exact layout may contain minor inaccuracies on our part, the overall structure should be roughly correct. For easier orientation, the following diagram illustrates how the individual structures are nested within each other:&nbsp;</p>

<p>At this point, it should be clear how the scan pattern maps onto the searched structure. The 32-byte match covers the <code>std::string</code> tag <code>v20\x00</code> and the beginning of the <code>Key</code> object up to and including <code>algorithm_</code>. The pointer at offset +32 from the start of the match then lands precisely on <code>key_.begin</code>, the first member of <code>std::vector&lt;uint8_t&gt;</code> that holds the encrypted <code>v20_master_key</code>.&nbsp;</p><p>Matches from all threads are collected into a shared buffer and subjected to a majority-voting scheme: candidates consisting mostly of zeroes are discarded, the rest are pairwise-compared, and each is scored by the number of identical copies found. This voting is performed independently for each browser process, producing one best candidate per process.&nbsp;</p><h2>Decrypting the v20_master_key via APC Injections&nbsp;</h2><p>For each browser process that produced a match, Vidar now holds a candidate address pointing to a potential encrypted <code>v20_master_key</code>. However, as already noted, since the key is protected with <code>CryptProtectMemory</code> using <code>CRYPTPROTECTMEMORY_SAME_PROCESS</code>, it can only be decrypted by invoking <code>CryptUnprotectMemory</code> from within the browser process itself. Vidar solves this by injecting an Asynchronous Procedure Call (APC) into the live browser process.&nbsp;</p><p>Vidar supports two APC injection methods, selected based on whether ESET or Bitdefender is detected on the system. If either of these products is present, Vidar uses the first method, which it refers to as “classic” (based on decrypted strings) – it creates a suspended thread in the target browser via <code>CreateRemoteThread</code> (with <code>NtTestAlert</code> as the thread start address and the <code>CREATE_SUSPENDED</code> flag), queues an APC using <code>NtQueueApcThread</code>, resumes the thread, and then waits for it to complete via <code>WaitForSingleObject</code> with a randomized timeout. When the thread resumes, it calls <code>NtTestAlert</code>, which flushes the APC queue and executes the injected routine.&nbsp;</p>

<p>If neither product is detected, it uses the “special” method – it finds an existing thread in the target browser using a combination of <code>CreateToolhelp32Snapshot</code> and <code>Thread32First/Thread32Next</code>, opens it via <code>NtOpenThread</code>, and calls <code>NtQueueApcThreadEx2</code> with the <code>QUEUE_USER_APC_FLAGS_SPECIAL_USER_APC</code> flag. Unlike regular APCs, special user APCs execute immediately. Therefore, the target thread does not need to be in an alertable wait state.&nbsp;</p>

<p>In both cases, the APC routine to be executed is <code>CryptUnprotectMemory</code>, called with the following three arguments: the address of the encrypted <code>v20_master_key</code> candidate, its size (32 bytes), and <code>CRYPTPROTECTMEMORY_SAME_PROCESS</code> for the <code>flags</code> parameter.&nbsp;&nbsp;</p><p>Since <code>CryptUnprotectMemory</code> decrypts the data in place, once the APC executes, the key is decrypted directly in the live browser's memory. To read it, Vidar creates a second fork of the browser process and reads the key from the same address using <code>NtReadVirtualMemory</code>. It then compares the result against a snapshot of the encrypted key taken from the first fork before the APC call – if the data is unchanged, decryption failed, and Vidar moves on to the next browser process’s candidate.&nbsp;</p><p>If the data differs, Vidar uses the same second fork to perform an additional verification: it scans the forked process’s memory for the byte sequence <code>v20</code> and, treating each match as a potentially ABE-encrypted entry (cookie, password), attempts AES-256-GCM decryption with the key candidate using <code>BCryptDecrypt</code> (successful GCM tag verification confirms that the key is correct).&nbsp;</p><p>Whenever the data has changed (indicating that decryption of the key took place), Vidar re-encrypts the key in the browser’s memory by injecting another APC with <code>CryptProtectMemory</code> as the routine, preserving the browser’s state. If no candidate produced a successful decryption (i.e., the data remained unchanged after every APC call), Vidar takes a more aggressive approach: it terminates all browser instances, restarts the browser, and repeats the entire scan-decrypt-verify cycle.&nbsp;</p><p>By abusing APC injections instead of the more traditional approach of injecting code via <code>NtWriteVirtualMemory</code> that performs the decryption, Vidar trades one suspicious behavior for another. APC injections are arguably less common and may thus slip past some detection systems, though they are still well-known techniques monitored by AV and EDR solutions. But that is the nature of ABE bypasses – each has its own advantages and disadvantages, and that’s exactly why infostealers keep inventing new ones. &nbsp;</p><h2>Indicator of Compromise (IoC)&nbsp;</h2><p>459daa809751e73f60fbbe4384a7d1653c36bb06945e4eb3635270924241100a (Vidar 2.1)&nbsp;</p>

A Technical Walkthrough of How Vidar Defeats Application-Bound Encryption

Inside Vidar’s ABE Bypass: From Memory Scanning to APC Injections

<p>You have a summer flight booked. You have seen the headlines about jet fuel shortages, cancelled routes and higher travel costs. Then a text message arrives: your flight has been affected, and you need to click a link to confirm your refund or rebook before the offer expires.&nbsp;</p><p>That message feels plausible because the situation around it is real. In April, <a href="https://www.iata.org/en/pressroom/2026-releases/2026-04-17-01/" target="_blank" rel="noreferrer noopener">IATA warned</a> that Europe could start seeing flight cancellations by the end of May if jet fuel shortages materialized. Airlines and governments have since been trying to reassure travelers, while also publishing guidance on passenger rights, refunds and re-routing.&nbsp;&nbsp;</p><p>That is exactly the kind of confusion scammers like. They do not need to cause the disruption, they only need to arrive at the right moment, with the right brand logo and the right sense of urgency.&nbsp;</p><h4>Why travel disruption works so well as a scam hook&nbsp;</h4><p>Most scam messages fail because they arrive out of context. A random refund email from an airline you never use is easy to ignore. A refund message from the airline you are flying with next week, during a period of public travel disruption, is different.&nbsp;</p><p>The scammer’s job is to make you think: “This could be real.”&nbsp;</p><p>That can happen in several ways. You might receive a fake cancellation email that links to a refund form. You might search for an airline’s customer service number and land on a fake support page. You might post publicly on social media asking an airline for help, then receive a reply from an account that looks official. Or you might get a WhatsApp message that knows your hotel name, travel dates or booking reference.&nbsp;</p><p>Each version uses the same pressure point: you are worried about losing money, losing your flight or being stranded.&nbsp;</p><p>Criminals are already using disruption this way. In March, <a href="https://www.theguardian.com/money/2026/mar/15/travel-scam-airline-accounts-fake-refunds-iran-war-flight-disruption" target="_blank" rel="noreferrer noopener">The Guardian reported</a> that fake airline support accounts were targeting travelers affected by Middle East flight disruption. Some victims were looking for help or refunds, then received replies from accounts pretending to represent airlines. The scam moved into direct messages, where victims were asked for details and sent links that led to money being taken instead of refunded.&nbsp;&nbsp;</p><p>The jet fuel story gives scammers another pretext. A message can claim that your flight was cancelled, your fare changed, your fuel surcharge failed, or your refund must be claimed within a few hours. None of those claims needs to be true to be effective.&nbsp;</p><h4>The scam may start before the message arrives&nbsp;</h4><p>A fake travel message becomes much harder to spot when it includes real information.&nbsp;</p><p>This is the idea behind <a href="https://www.gendigital.com/blog/insights/research/reservation-hijack-scam" target="_blank" rel="noreferrer noopener">Reservation Hijack scams</a>, a form of targeted phishing where cybercriminals use real booking details to make a message look legitimate. In some cases, attackers may use information exposed through breaches or compromised travel systems. In other cases, they collect details from emails, social media posts, previous leaks or fake customer service interactions. Gen has previously described Reservation Hijack scams as scams that use real hotel booking details to make fraudulent payment or verification requests feel authentic.&nbsp;&nbsp;</p><p>That distinction matters. A scam message does not need your credit card number to fool you. Knowing your name, your destination, your travel dates and your booking platform may be enough.&nbsp;</p><h4>What these scams can look like&nbsp;</h4><p>A travel disruption scam usually does not begin with a strange offer. It begins with something boring and administrative. That is part of the trick.&nbsp;</p><p>You may see messages like:&nbsp;</p><p>“Your flight has been cancelled due to fuel supply issues. Claim your refund here.”&nbsp;</p><p>“Your rebooking is pending. Confirm passenger details within two hours.”&nbsp;</p><p>“Additional airport tax or fuel surcharge is required to keep your booking.”&nbsp;</p><p>“Your hotel reservation will be cancelled unless payment is verified.”&nbsp;</p><p>“Due to high call volume, please continue this request on WhatsApp.”&nbsp;</p><p>The exact wording changes, but the structure is familiar. There is a problem, a deadline and a link. The message may also move you away from the official channel into SMS, WhatsApp, Telegram, direct messages or a phone call. Once that happens, the scammer controls the conversation.&nbsp;</p><p>There is another detail worth watching: some messages do not ask for money immediately. They start by asking for your booking reference, last name, phone number or one-time password. That can still be dangerous. Those details can help scammers access a booking, impersonate you to customer support, reset an account or make the next message more convincing.&nbsp;</p><h4>Your real passenger rights can be used against you&nbsp;</h4><p>If an airline cancels your flight, you may have rights to a refund, re-routing or assistance, depending on where you are travelling and the rules that apply. The European Commission said passengers affected by cancellations continue to have rights to reimbursement, re-routing or return, airport assistance and compensation for last-minute cancellations in relevant circumstances. It also said airlines cannot retroactively add fuel surcharges to already published final ticket prices.&nbsp;&nbsp;</p><p>That information is useful for travelers, but it is also useful for scammers.&nbsp;</p><p>A fake refund message becomes more believable when people already know refunds are possible. A fake rebooking link becomes more believable when airlines are genuinely changing schedules. A fake “fuel surcharge” demand becomes more dangerous when fuel prices are in the news, even though legitimate retroactive charges may not be allowed in many cases.&nbsp;</p><p>This is why the safest route is not to judge the message only by whether the story sounds plausible. During travel disruption, many scam stories will sound plausible. Judge the channel instead.&nbsp;</p><h4>How to check before you click&nbsp;</h4><p>Start from the airline or booking platform’s official app or website. Do not use the link in the message. Open the app yourself, type the website address yourself, or use the contact details listed on your original booking confirmation.&nbsp;</p><p>Check whether the same cancellation, refund or payment request appears inside your account. If the message is real, the airline or hotel should be able to confirm it through an official channel.&nbsp;</p><p>Be careful with social media support. If an account replies to your public complaint, check whether it is linked from the airline’s official website. Look at the handle carefully. Fake support accounts often copy logos and names, but have small differences in spelling, low follower counts or recently created profiles. The Guardian reported that fraudsters often scan social media for passengers trying to contact legitimate airline accounts and reply to them first, which makes the scam harder to spot.&nbsp;&nbsp;</p><p>Do not share one-time passwords, payment card details or login credentials with anyone who contacts you unexpectedly. A real airline or hotel does not need your banking OTP to send you a refund.&nbsp;</p><p>Be especially suspicious of pressure. “You have 30 minutes to claim your refund” is not customer service. It is a tactic.&nbsp;</p><h4>What to do if you already clicked&nbsp;</h4><p>If you entered payment details, contact your bank or card provider immediately. Ask whether the transaction can be blocked or reversed, and request a new card if needed.&nbsp;</p><p>If you shared login details for an airline, hotel or booking platform, change the password from the official site or app. Use a unique password, not one you use elsewhere. Turn on two-factor authentication where it is available.&nbsp;</p><p>If you shared a one-time password or authentication code, assume the account may have been accessed. Check your booking details, payment methods and recent account activity.&nbsp;</p><p>Report the scam to the airline, hotel or booking platform being impersonated. If the scam came through social media, report the account as impersonation. If money was taken, report it to the relevant fraud authority in your country.&nbsp;</p><h4>The real lesson for summer travel&nbsp;</h4><p>Travel disruption changes how people behave. They search for support numbers in a hurry. They post publicly because customer service queues are long. They accept strange instructions because they are worried about losing a flight or refund.&nbsp;</p><p>Scammers build around that behavior.&nbsp;</p><p>The safest assumption is simple: if a message about your flight, hotel or refund creates urgency and gives you a link, pause. Go back to the official source. A real cancellation will still be there when you check through the airline or booking platform. A scammer needs you to act before you do.&nbsp;</p>

Travel disruption gives scammers the one thing they need most: a believable reason to rush you

Your flight was cancelled. Is the refund message real? 

<p>A fake job interview page is easier to trust than a fake ticket shop.</p><p>In samples reviewed by Gen threat researchers, scammers used branded hiring pages that looked like ordinary recruitment flows: a company logo, a recruiter profile, a 30-minute meeting, and a button to continue with Google or Facebook. There was no attachment to open and no software to install. The credential theft attempt sat inside a step many job applicants already expect: signing in to schedule a call.</p><p>FIFA is an obvious lure ahead of the 2026 World Cup. On May 22, ESET reported fake FIFA-themed websites that copied ticket and merchandise flows to steal money and personal data. Our researchers later found another FIFA-themed domain, hxxps://fifa-mg[.]shop, which followed a naming pattern not mentioned in that report. Domains like these can be short-lived, often appearing for hours or days before they are blocked, abandoned, or taken down.</p><p>Our researchers also found a different kind of FIFA lure: hxxps://fifahiring[.]com, a fake hiring page that encouraged users to schedule a call with an alleged FIFA recruiter. When a user tried to register with a personal Gmail address, the page asked for a business email instead. The page was steering victims toward credentials with more value: accounts that could provide access to a company environment.</p>

<h4>The FIFA hiring page did not point to FIFA</h4><p>The fake page looked believable at first glance.</p>

<p>It used FIFA branding, presented a recruiter identity, and copied parts of the experience users see on legitimate recruiting and scheduling platforms. The recruiter’s name and photo appeared to match a real LinkedIn profile, which made the page feel more credible. For publication, we should keep that person’s identity redacted.</p><p>The domain did not match FIFA’s real hiring infrastructure. FIFA’s legitimate careers pages are jobs.fifa.com and fifa.pinpointhq.com. The fake page used neither. It also loaded the favicon from the real FIFA recruitment site hosted at pinpointhq.com, giving the page a small visual cue borrowed from the legitimate service.</p><p>Other signals pointed in the same direction. The domain and certificate were newly created, from May 23. The site used commodity hosting infrastructure, including Vercel and Render, rather than a corporate environment. Those signs are not enough on their own, but they fit the rest of the evidence.</p><p>The login flow was the clearest part. Credentials were posted to:</p><p>fifeq2026eqbackeq[.]onrender[.]com/api/login</p><p>The Google sign-in prompt was not a real Google authentication window. It was rendered inside the page itself. The visible controls and links did nothing, and the page did not send the user into a genuine Google sign-in flow. According to the analysis, the only Google asset loaded was the favicon, apparently to make the fake window look familiar.</p><p>A page can look like it opened a Google login without ever handing control to Google.</p><p>Researchers also observed hxxps://careers-fifahiring[.]com, which later became inactive, and hxxps://fifajobs[.]com, which showed the same content and was indexed by Google.&nbsp;</p><h4>The recruitment lure went beyond FIFA</h4><p>The FIFA page was one version of a wider recruitment phishing pattern. The brand can change. The flow stays familiar: recruiter profile, meeting prompt, business email, fake sign-in.</p><p>Researchers found similar fake hiring pages abusing other major brands, including <strong>Heineken, Hilton, Coca-Cola, Netflix, PepsiCo, Delta,&nbsp;</strong>and<strong> Spotify</strong>. In the Heineken case, the page appeared to use the identity of someone who, according to LinkedIn, really works as a recruiter at the company.</p>

<p>Additional hunting found two other recruitment-themed kits:</p><p>hxxps://aquent-talent-jobs[.]com<br>hxxps://hays-talent-opportunities[.]com</p><p>The Hays-themed version targeted Facebook credentials instead of Google credentials. Researchers assessed that the Aquent and Hays pages shared code, although they differed from the earlier FIFA examples.</p>

<p>This flexibility makes the campaign harder to frame as a single World Cup scam. FIFA provides the timely hook, but the mechanism is recruitment phishing. A scammer can swap the logo, recruiter name, and sign-in provider while keeping the same basic path to the victim’s credentials.</p><h4>Why fake recruitment pages work</h4><p>Recruitment gives attackers a clean excuse to ask for things that might otherwise raise suspicion.</p><p>A candidate expects to click a scheduling link. They expect a recruiter profile. They expect a calendar prompt. In some cases, they may also expect to use a work email, especially for corporate, contractor, or partner-facing roles.</p><p>The fake login window turns that ordinary flow into credential theft. Users are used to “Continue with Google” and “Continue with Facebook” buttons, but the button itself proves nothing. A genuine authentication flow should take the user to the provider’s domain and controls. A fake page can draw a convincing copy while keeping the victim inside the attacker-controlled site.</p><p>The business email prompt is also a warning sign. A page that rejects a personal email and asks for a work address may be trying to raise the value of the stolen account.</p><h4>What job seekers should check before signing in</h4><p>Start from the company’s official careers page, not from a link in a message, ad, search result, or forwarded post. For FIFA, that means checking jobs.fifa.com or fifa.pinpointhq.com, not trusting a domain because it contains “fifa,” “career,” “hiring,” or “jobs.”</p><p>Look closely at the domain before entering credentials. Scam pages often add plausible hiring words around a brand name: career, talent, jobs, hiring, portal, or connect. A polished page on a new domain is still a new domain.</p><p>Treat the sign-in step as the real checkpoint. If a page offers Google or Facebook login, check whether the flow actually opens a real provider-controlled authentication page. A fake window embedded inside the original site, broken controls, inactive links, or a provider logo used only as decoration should stop the process.</p><p>Use security software that includes web and phishing protection. These tools can block known malicious pages before they load, which is especially useful when scam domains look polished, appear in search results, or are shared through otherwise legitimate channels.</p><h4>What companies can do</h4><p>Recruitment pages are public by design, which makes them easy to copy.</p><p>Security teams should monitor for newly registered domains combining their brand with hiring-related terms. They should also watch for pages that reuse favicons, recruiter photos, job descriptions, and calendar-booking language from legitimate hiring flows.</p><p>HR and recruiting teams should make the official hiring path easy to verify. Candidates should not have to guess whether a domain is legitimate. A clear careers page, consistent recruiter communication, and warnings about unofficial scheduling links can remove some of the ambiguity attackers rely on.</p><h4>Conclusion</h4><p>The fake FIFA hiring page worked because it did not feel unusual. It looked like a normal step in a hiring process.</p><p>Attackers do not need to invent new behavior when they can copy one people already trust. A branded scheduling page, a recruiter profile, and a familiar sign-in button can be enough to move a victim from interest to credential entry.</p><p>The decision point is the login. Before entering a work email or password, check the domain, check where the authentication flow really goes, and verify the role through the company’s official careers site. Security software with web and phishing protection adds another layer, especially against short-lived scam pages that may only stay online for hours or days.</p><p><strong>IOCs:</strong></p><p>hxxps://fifahiring[.]com<br>hxxps://careers-fifahiring[.]com<br>hxxps://fifajobs[.]com<br>hxxps://fifa-mg[.]shop<br>hxxps://heineken-careers[.]com<br>hxxps://aquent-talent-jobs[.]com<br>hxxps://hays-talent-opportunities[.]com<br>fifeq2026eqbackeq[.]onrender[.]com/api/login</p>

Scammers are copying recruitment and calendar-booking flows to make fake Google and Facebook sign-ins look routine. 

Fake hiring pages abuse FIFA and other major brands to steal work credentials 

Threat Research Team Lead

<p>Since January 2026, we have detected 7.4 million malicious incidents tied to residential proxy traffic, affecting 572,000 users in our telemetry. In this model, the household whose connection is being used is often not the buyer of the traffic. It is the exit point.</p><p>That is the uncomfortable part of residential proxy networks. A home router, laptop, phone, smart TV, or other always-on device can quietly become part of a commercial network that routes strangers’ internet traffic through ordinary consumer IP addresses. To the websites on the other end, that traffic looks as if it came from a real household, because it did.</p><p>The technology itself is not inherently malicious. Businesses use residential proxies for market research, ad verification, brand protection, security testing, and services that need to see the web as a real user would. But the same feature that makes these networks useful also makes them attractive for abuse: traffic from a household IP address is hard to block without risking false positives against legitimate users.</p><p>The problem for consumers is simpler. Many people do not realize their device or connection can be enrolled into this kind of network at all. Some users opt in through pay-for-bandwidth apps. Others are enrolled through “free” VPNs, bundled software development kits inside unrelated apps, or unwanted software that installs proxy components without meaningful consent.</p><p>Here is how the market works, who pays for it, and what it can cost the household that unknowingly hosts it.</p><h2>What is a residential proxy</h2><p>A residential proxy is an internet connection – typically a home laptop, phone, smart TV, or router – that has been enrolled into a third-party network and is being used to route someone else's traffic. To the rest of the internet, that traffic looks like it is coming from an ordinary household IP address assigned by a consumer ISP, not from a datacenter or&nbsp;VPN provider.</p><p>Residential proxy networks are sold commercially. The model is two-sided: some people pay to tunnel their traffic out through someone else's connection (much like a VPN, except the exit point is a real home), while others get paid to provide those exit endpoints. Some are structured as paid peer-to-peer networks, where any participant's connection can serve as an exit for any other.</p><p>Buyers pay for access to pools of millions of these "real user" IPs because they are extremely difficult to block, or rather, blocking them carries real consequences: the traffic originates from genuine households, so any block risks shutting out a legitimate user – effectively a false positive.</p><p>Common buyers include market research firms, price-comparison services, brand-protection vendors, security teams testing their own defenses, and consumer privacy tools. At the abusive end of the market, the same infrastructure used by operators running automated purchasing bots, scrapping campaigns, ad fraud, credential stuffing, phishing and other attacks where hiding the true origin of the traffic matters. Demand is also being shaped by large-scale web scraping, including&nbsp;<a href="https://blog.includesecurity.com/2026/06/the-smart-tv-in-your-livingroom-is-a-node-in-the-aiscraping-economy/">scraping for AI training data</a>. As anti-bot systems become better at identifying traffic from datacenters and known VPN providers, residential IP addresses become more attractive because they look like ordinary users. That does not make every residential proxy user malicious. It does mean consumers may be carrying traffic for businesses and actors they have never heard of.</p><h2>How consumer devices end up in these networks</h2><p>There are several ways a home device can become part of a residential proxy network. Some are explicit. Others are easy to miss.</p><p>The most obvious route is the pay-for-bandwidth model. Apps such as Honeygain, IPRoyal Pawns, and PacketStream pay users to share their internet connection. The user opts in, but they may not understand who will buy access to that connection later, what kind of traffic will pass through it, or what happens if that traffic triggers abuse reports.</p><p>A second route is the “free” VPN or proxy app. Instead of charging a subscription, the app monetizes the user’s connection by reselling bandwidth. In practice, the user may think they are getting a privacy tool while also becoming infrastructure for other people’s traffic.</p><p>A third route is through bundled software development kits, or SDKs. A developer adds a third-party component to an otherwise unrelated app, such as a flashlight, wallpaper, game, or utility. The developer gets paid when the app is active. The user sees the host app, not the proxy network behind it.</p><p>The fourth route is malware or potentially unwanted software. In those cases, the proxy component is installed silently or deceptively, with no meaningful user consent at all.</p><h2>Why the "consent" is rarely meaningful</h2><p>Even when consent technically exists, it is often not the kind of consent most people would recognize.</p><p>The disclosure may be buried in a long terms-of-service document. The wording may be vague, with phrases such as “share your unused bandwidth,” “support the app,” or “join our network.” These phrases do not clearly tell the user that arbitrary third parties may route traffic through the user’s home IP address.</p><p>There is also the question of downstream use. Users are rarely told who buys access to the network or what those buyers do with it. Their connection could be used for benign market research. It could also be used for scraping, automated account creation, ad fraud, credential stuffing, or phishing infrastructure.</p><p>The problem gets worse when the proxy component sits inside another app. The host app’s privacy policy may mention a partner SDK by brand name, but that still does not make it clear to a normal user that their device can become a proxy endpoint.</p><p>Uninstalling the visible app may not always resolve the issue cleanly either, especially when proxy components are installed separately or bundled with other unwanted software.</p><h2>The risks consumers actually carry</h2><p>When a household device becomes a residential proxy node, the user takes on risks created by someone else’s traffic.</p><p>The first risk is attribution. Abusive, fraudulent, or illegal activity routed through the device appears to come from the household’s IP address. ISP abuse notices, platform bans, fraud checks, and law enforcement requests point first to the subscriber, not to the person who bought the proxy traffic.</p><p>The second risk is performance. Continuous third-party traffic can consume bandwidth, slow the home network, hit data caps, or violate ISP terms of service. The user may only notice that the internet feels slower, a bill is higher, or a service suddenly blocks access.</p><p>The third risk is security exposure. Proxy clients run persistent background processes and maintain network connections so they can relay traffic. That adds always-on networking software to the device, often with limited visibility for the user.</p><p>The fourth risk is reputation. A home IP address used for abuse can end up on blocklists used by banks, retailers, streaming services, and online platforms. The result can be account friction, failed logins, extra verification steps, or outright blocking from services the household actually uses.</p><p>There is also a family angle. A child or another household member may install a free game, VPN, or utility without understanding the consequences. The legal, financial, and reputational risk still lands on the account holder.</p><h2>What our telemetry shows</h2><p>Since the beginning of 2026, we have detected 7.4 million malicious traffic incidents associated with residential proxy traffic, affecting 572,000 unique users in our user base.&nbsp;<br>This is not a measurement of the entire residential proxy market. It reflects what we observe in our telemetry: malicious traffic, detections, and related activity affecting protected users. The real footprint is far larger, because residential proxy networks span major consumer platforms and many devices outside our visibility.</p><p>The activity is global, but it is concentrated in a smaller set of countries. India leads by a wide margin, with roughly 83,000 affected users, followed by Vietnam with 61,000 and Brazil with 39,000. The Philippines (23,000), Poland (18,000), Indonesia (18,000) and Thailand (14,000) form a second tier, with Egypt, Spain, Ukraine, Argentina, Mexico and Italy each accounting for 10,000 to 13,000. The spread across South and Southeast Asia, Latin America, and Eastern and Southern Europe reflects where the host apps that carry this software are most widely installed.</p><p>That geographic spread likely reflects a combination of app distribution, local install patterns, user appetite for free or pay-for-bandwidth apps, and the economics of bandwidth resale. It should not be read as a simple ranking of where residential proxy abuse originates.</p><p>The chart below breaks down the threats we observed in this proxy-related traffic. Two categories dominate: phishing and malicious advertising. Behind them sits a long tail of consumer-facing fraud, including e-shop scams, generic scams, financial scams, and fake-tutorial pages, alongside outright malware such as trojans and other malicious traffic.&nbsp;</p>

<p>In the malicious proxy traffic we observed, scams and malware dominate. The important point for consumers is not only that their connection may be used by someone else. It is that, when abuse happens, their household IP address can be the return address.</p><h2>What consumers can do</h2><p>Most people will not identify a residential proxy component by name. But there are practical warning signs.</p><p>Review “free” VPNs, proxy apps, bandwidth-sharing apps, and utilities from unknown publishers. Check whether they mention bandwidth sharing, peer-to-peer networking, traffic routing, or network participation in their terms. If an app offers payment for leaving your device online, assume your connection may be resold unless the provider explains exactly how traffic is vetted and who can buy access.</p><p>On phones and computers, remove apps you do not recognize or no longer use. On home routers, check the list of connected devices and look for anything unfamiliar. If your ISP sends abuse notices, websites start blocking you, or your home IP address suddenly fails fraud checks, a proxy component is one possible explanation.</p><p>Security software can also help by detecting unwanted proxy clients, bundled components, and related malicious activity. But this should not be a guessing game for consumers. Software that turns a household connection into a commercial exit node should be named clearly and made easy to remove.</p><h2>The takeaway&nbsp;</h2><p>With residential proxiesthe user’s connection becomes an infrastructure for someone else’s business.</p><p>The issue is not that residential proxy technology exists. It has legitimate uses. The issue is whether people know when their devices are part of it, understand what kind of traffic may pass through their connection, and have a real choice to opt out.</p><p>The fix is not to pretend consumers will read every EULA. This software should be named clearly, shown plainly, and made easy to remove before a household connection becomes someone else’s infrastructure.</p>

Your home connection could be routing traffic for strangers. Here's how residential proxy networks work, how devices get enrolled and what our telemetry reveals about the risks for consumers.

Who's Really Using Your Home Internet Connection?

<h4>Key Points&nbsp;</h4><ul><li data-list-item-id="e43a143fd054561c50dba51071686adff">Gen Threat Labs has been tracking GoFlateLoader, a widespread Golang loader used to deliver multiple infostealers, including Amatera, Remus, Lumma, Vidar and StealC.&nbsp;</li><li data-list-item-id="e3d3b5d0814ea5b26aa75a8d3d6013a39">GoFlateLoader appears both in x86 (32-bit) and x86-64 (64-bit) variants, matching the bitness of the payload it is supposed to execute.&nbsp;</li><li data-list-item-id="e51ccafcfb8c418d894aeb685004a0ba5">The loader is designed for in-memory payload execution and is deliberately inflated with a massive PE overlay to hinder detection</li><li data-list-item-id="ec4bafef8a1113d24bc2b4b3a943228d1">The two main delivery paths are via supposedly cracked software and a <a href="https://research.checkpoint.com/2026/impersonation-click-hijacking-and-tds-inside-a-malware-distribution-ecosystem/" target="_blank" rel="noreferrer noopener">malicious TDS recently documented by Check Point Research</a>, which may redirect users to dedicated landing pages serving password-protected archives containing GoFlateLoader.&nbsp;</li></ul><h4>Introduction&nbsp;</h4><p>Not every threat that matters is technically sophisticated, and that is also the case with GoFlateLoader, which is a rather simple loader written in Go, whose sole purpose is to decode and execute the payload in memory. What stands out the most is not what the loader does but rather what it does not do – it comes without anti-debugging, anti-VM, or sandbox-evasion checks, and also lacks API hashing or CFG obfuscation, the kind of tricks that loaders almost always come with. Instead, GoFlateLoader relies on one of the simplest yet still effective tricks to stay under the radar – it appends a massive PE overlay at the end of the file, deliberately inflating the binary's size (hence the name GoFlateLoader).&nbsp;</p><p>Nevertheless, it is important to understand that malware does not necessarily need to be elegant or stealthy. In the end, the only thing that matters to attackers is whether it can successfully deliver the final payload. And if that is the only metric, GoFlateLoader appears to be working fairly well for its operators, as we continue to see it widely distributed across our user base. Since the beginning of April, we have protected more than 33,000 unique users from it, with the most affected countries including Brazil, India, Argentina, Mexico, Turkey and Spain.&nbsp;</p>

<h4>GoFlateLoader’s Execution Flow&nbsp;</h4><p>If we strip away the obfuscation noise that the Go compiler and the author’s decoy code add, the loader’s execution flow is short and linear:&nbsp;</p><ul type="disc"><li data-list-item-id="efa51af3b2859fd9c684efca0c82d3b66">Copy the encoded payload blob from the <code>.rdata</code> section onto the stack.&nbsp;</li><li data-list-item-id="e879bb970c6d1a81b8a42512222aceaa4">Decode the payload using a small, multi-stage, custom byte-level transformation into a valid PE.&nbsp;</li><li data-list-item-id="ebff4f340af15b75cbea0d682b26b7645">Parse the PE headers of the decoded payload (image base, image size, sections, data directories, etc.).&nbsp;</li><li data-list-item-id="e37fb26cad3d18a4a0c8bf9b2595d661f">Allocate an RWX memory region using <code>VirtualAlloc</code> with <code>MEM_COMMIT | MEM_RESERVE</code> and <code>PAGE_EXECUTE_READWRITE</code> flags, trying the payload’s preferred <code>ImageBase</code> first and falling back to an OS-assigned address if that fails.&nbsp;</li><li data-list-item-id="ebbde6d77cdc942c0a6bac79f4f8a6c28">Map the decoded payload into the allocated memory region by copying the PE headers first, then walking the section table and writing each section to its target virtual address.&nbsp;</li><li data-list-item-id="ed16738229e0f5c70a981c0c5f9b715f9">Apply relocations (only if preferred base mapping fails).&nbsp;</li><li data-list-item-id="e76cde4bae1be6c21b897c350c6fd15db">Resolve imports by walking the standard <code>IMAGE_IMPORT_DESCRIPTOR</code> table and rebuild the IAT in place via <code>LoadLibrary</code> and<code> GetProcAddress</code>.&nbsp;</li><li data-list-item-id="e786887a3d34fc7ce344ee8375944799e">Transfer execution to the final payload using Go’s <code>syscall.Syscall</code>.&nbsp;</li></ul><p>&nbsp;</p><p>This is essentially a textbook example of manual PE loading with the payload reconstructed and executed entirely in memory so that it never touches the disk.&nbsp;&nbsp;</p>

<p>Notably, GoFlateLoader transfers execution to the final payload via <code>syscall.Syscall</code>. In Go, <code>syscall.Syscall</code> has the signature <code>Syscall(trap, nargs, a1, a2, a3)</code>, where <code>trap</code> is the function pointer to invoke, <code>nargs </code>is the argument count, and <code>a1</code>, <code>a2</code>, and <code>a3</code> are the first three arguments passed to the target function. Here, trap is set to point to the final payload’s entry point, <code>nargs</code> is set to <code>1</code>, and since the execution is transferred to that entry point, the remaining arguments serve only as filler values and are never used by the invoked payload. In other words, GoFlateLoader is not issuing a <code>syscall</code> at all, but abusing <code>syscall.Syscall</code> as a generic call gate to hand control to the payload.&nbsp;&nbsp;</p><p>It is worth emphasizing that GoFlateLoader consistently sets these arguments to the hardcoded values <code>1</code>, <code>2</code>, <code>3</code>, and <code>4</code>, which is unusual enough to stand out as a potential detection opportunity (combined with other patterns).&nbsp;</p>

<p>The loader also carries substantial junk/decoy code, which varies across builds and serves no purpose other than padding the control flow and complicating static analysis.&nbsp;&nbsp;</p><p>&nbsp;</p><h4>Inflated PE Overlay&nbsp;</h4><p>GoFlateLoader’s defining characteristic is its massive size (typically 700-950 MB), caused by an artificially inflated PE overlay appended to the original loader.&nbsp;</p>

<p>This is a deliberate design choice intended to bypass detection, as excessively large executable files may pose challenges for AVs and EDRs, primarily due to performance and resource constraints. As a result, to preserve performance and avoid noticeable impact to end users, these solutions often enforce practical file-size limits for deep scanning and/or emulation.&nbsp;</p><p>The same logic extends to automated analysis pipelines – bloated files frequently cause timeouts during heuristic analysis and effectively prevent the sample from being uploaded to cloud-based sandboxes or threat intelligence platforms, which enforce their own strict upload limits to manage bandwidth and storage costs. A prime example is VirusTotal, which enforces a strict 650 MB upload limit. The fact that GoFlateLoader consistently sits just above this threshold strongly suggests that VirusTotal is one of the platforms it specifically aims to evade.&nbsp;&nbsp;</p><p>In most cases, GoFlateLoader’s PE overlays are filled with null bytes, though we have also observed builds with random padding.&nbsp;&nbsp;</p>

<p>Crucially, adding such a PE overlay comes at virtually no distribution cost for attackers, as the inflated data compresses to a fraction of its original size (assuming constant padding).&nbsp;</p><p>&nbsp;</p><h4>Delivered Final Payloads&nbsp;</h4><p>The final payloads distributed through GoFlateLoader are predominantly information stealers, with the most prevalent currently being Amatera, <a href="https://www.gendigital.com/blog/insights/research/remus-64bit-variant-of-lumma-stealer" target="_blank" rel="noreferrer noopener">Remus</a>, and Lumma. Beyond these, we have also observed it distributing Vidar, StealC, and SvitStealer.&nbsp;</p><p>GoFlateLoader comes in both x86 and x86-64 variants, with each variant matched to the architecture of the payload it is intended to execute.&nbsp;&nbsp;</p><p>As for how GoFlateLoader binaries are distributed, we have observed at least two notable delivery paths. The first is through supposedly cracked software. The second involves the payload being served via <a href="https://research.checkpoint.com/2026/impersonation-click-hijacking-and-tds-inside-a-malware-distribution-ecosystem/" target="_blank" rel="noreferrer noopener">the malicious TDS recently described by Check Point Research</a>, which redirects users to a landing page that offers a downloadable archive and separately displays the password required to extract it. This approach provides several advantages for the threat actor. First, compression significantly reduces the binary size due to the constant-padded PE overlay. Second, because the archive password is displayed separately on the landing page, it makes it harder for AV and EDR solutions to obtain it and decrypt the archive. As a result, the payload may remain concealed until the victim manually extracts it.&nbsp;</p><p>&nbsp;&nbsp;</p><h4>Summary&nbsp;</h4><p>GoFlateLoader is a reminder that prevalence and sophistication are not the same thing. At its core, it is a rather simple manual in-memory PE loader written in Go, with no novel anti-analysis tricks under the hood. Whatever evasion it achieves comes not from obfuscation or other anti-analysis tricks but from its size – the appended PE overlay is built to slip past size-constrained scanners and automated analysis pipelines. Yet, despite its low level of sophistication, GoFlateLoader remains an active and relevant threat, used to deliver a wide range of prevalent information stealers.&nbsp;&nbsp;</p><p>Gen products protect our users against both GoFlateLoader and the payloads it delivers.&nbsp;</p><p>&nbsp;</p><h4>Indicators of Compromise (IoCs)&nbsp;</h4><p>Note: The files listed in the IoCs that are not archives all exceed 650 MB in size and are therefore not available on VirusTotal.&nbsp;</p><p>b88c5744975d2abb447aecc6c090fee9f8580413f4612eecdc6ed1973e8a1739 (password-protected archive containing GoFlateLoader x64 variant loading Remus; pwd: 1234)&nbsp;</p><p>ed5ae7f36453c5a23e9868a5729d67e0549a11f6dea54f5f52d654a8f51d4902 (archive containing GoFlateLoader x64 variant loading Remus)&nbsp;</p><p>841c9297cb8a2e0ff89433d13c05bfc760eb2e98e251cb8fa785d2ad7cbac05f (archive containing GoFlateLoader x86 variant loading Amatera)&nbsp;</p><p>ece7c48eb411b24f26762ede83badb4a644c41d5777129381ac2541804d64fc2 (archive containing GoFlateLoader x86 variant loading Lumma)&nbsp;</p><p>421ce2d2f49c23bbe9f60ef3b9cd38d7eb912ce02e56a61837656210069bd9e2 (archive containing GoFlateLoader x64 variant loading Vidar)&nbsp;</p><p>121c2dc793b3873f75a29ec02241f94136de19c049382a50a50d0d5b99507073 (GoFlateLoader x64 variant loading StealC)&nbsp;</p><p>2415db5081cec9bfd14ad6da1a66169fd96f13a49010c319a73d1ed6fafd4efa (GoFlateLoader x64 variant loading Vidar)&nbsp;</p><p>d9917ade3b4c125a95b5d3e6343cde26145dfbf569bd7e2a843fd0c6fc8ddc28 (GoFlateLoader x64 variant loading Remus)&nbsp;</p><p>4cf6893756f441522b94b36f10e5de0e47aeed4743f95c51650746d1ecf97e3d (GoFlateLoader x64 variant loading SvitStealer)&nbsp;</p><p>8b89d6c9152d3aab97aadd515ecb69ca72654db2f25425759ba4b646853d737d (GoFlateLoader x86 variant loading Lumma)&nbsp;</p><p>90ce4ff9da23ac150da0a8e17930cab1e369aa349fdc1b65691b70369145664a (GoFlateLoader x86 variant loading Amatera)&nbsp;</p>

 Intentionally Inflated Go Binaries That Use Massive PE Overlays to Bypass Detection

GoFlateLoader: A Widespread Golang Loader Delivering Multiple Infostealers

Malware Researcher

<p>When we published the first part of this research, we said the investigation was still ongoing. That was not a closing line. We were already looking at the infrastructure, the signals behind the attacks, and the scale of the reservation data abuse we were seeing in our telemetry.&nbsp;</p><p>Then something else happened.&nbsp;</p><p>Friends, colleagues, and other contacts started forwarding us messages they had received from Booking.com. The messages warned that unauthorized third parties may have accessed information linked to their reservations. Shortly after, media outlets began reporting the same thing: Booking.com had notified affected customers, reset reservation PINs, and said the accessed information could include names, email addresses, phone numbers, booking details, and information shared with accommodations. Booking.com said financial information was not accessed from its systems.&nbsp;</p><p>The timing mattered, but not because it started our investigation. It mattered because it publicly confirmed the kind of reservation-data exposure our first article had described from the attack side.&nbsp;</p><p><a href="https://us.norton.com/blog/online-scams/reservation-hijacking-scam" target="_blank">Reservation Hijack scams</a> work because criminals do not have to guess. A traveler receives a message about a real booking. The message contains details that make sense: the right accommodation, the right trip context, sometimes the right contact information. The link then opens a fraudulent page built around the same accommodation.&nbsp;</p><p>A generic <a href="https://us.norton.com/blog/online-scams/what-is-phishing " target="_blank">phishing message</a> has to create trust from nothing. This scam steps into a relationship that already exists between the traveler, the booking platform, and the accommodation.&nbsp;</p><p>While those public warnings were appearing, Gen Threat Labs continued canvassing the data we had available: blocked URLs, fraudulent landing pages, SMS messages, emails, WhatsApp messages, in-app message evidence, and other signals connected to attacks we had already stopped. We used AI-assisted analysis to connect pieces that would otherwise remain scattered: messages, landing pages, accommodation names, URLs, templates, and infrastructure patterns. Human analysts reviewed the results and separated what we could prove from what we could only suspect.&nbsp;</p><p>The result is a much clearer picture.&nbsp;</p><p>We identified more than <strong>350 compromised accommodations</strong> linked to the Reservation Hijack scam flows, spread across <strong>50 countries</strong>. These were not abstract indicators or generic travel-themed pages. In the cases we analyzed, victims had already received reservation-specific information before being pushed to a fraudulent page customized around the accommodation tied to that booking.&nbsp;</p><p>That is the difference between ordinary travel phishing and this model. The attackers are not guessing who is traveling. They already have enough reservation context to make the fraud feel normal.&nbsp;</p><p>And they are doing it at scale.&nbsp;</p>

<h3>How we connected the evidence&nbsp;</h3><p>The second phase of our investigation was already underway when Booking.com’s customer notifications started circulating publicly.&nbsp;</p><p>Gen’s view of this activity comes from attacks we blocked before they could complete. No single signal tells the whole story. An SMS or WhatsApp message may show the <a href="https://us.norton.com/blog/emerging-threats/what-is-social-engineering " target="_blank">social engineering</a>. A URL may show the redirect path. A landing page may show the accommodation being impersonated. An in-app message may show where the attacker entered the trusted communication flow. A repeated page structure may link incidents that look separate at first.&nbsp;</p><p>Put together, those pieces show how reservation data moves from compromise to fraud.&nbsp;</p><p>AI helped us work through that evidence at scale. We used it to normalize accommodation names, cluster similar messages, compare landing-page structures, connect URLs with page content, and flag repeated patterns across channels. This was not “AI says these attacks are connected.” It was AI-assisted triage followed by human review.&nbsp;</p><p>From that process, we extracted and cleaned accommodation names from captured fraudulent landing pages and identified <strong>350 compromised accommodations</strong>.&nbsp;</p><p>We use “compromised accommodations” carefully here. It means reservation context tied to those accommodations was compromised and used in an attack flow we intercepted. The source of compromise may vary: a hotel account, a booking platform partner account, an email inbox, a property management system, a guest messaging workflow, or a third-party service provider.&nbsp;</p><p>The end result for the traveler is the same. Criminals had access to information that should have stayed inside the booking relationship.&nbsp;</p><p>This is also a conservative number. It only includes attacks where we had enough evidence to connect the flow to a specific accommodation. It does not include people who received a message and never clicked, attacks outside our telemetry, landing pages we did not capture, or cases where the accommodation name could not be reliably extracted.&nbsp;</p><p>So 350 is not the size of the problem. It is the part we could see clearly.&nbsp;</p><h3>From scam pattern to repeatable operation&nbsp;</h3><p>A single compromised hotel account can explain a few victims. A copied phishing kit can explain a short campaign. Hundreds of accommodation-specific scam flows across 50 countries point to something more organized.&nbsp;</p><p>The model we see is consistent.&nbsp;</p><p>Reservation context enters the fraud chain, sometimes through compromised accommodation-side accounts, inboxes, partner tools, or data obtained from other criminal actors. That context is then used to contact travelers with details that make the message feel legitimate.&nbsp;</p><p>The wording, the property, the country change. The logic does not.&nbsp;</p><p>That is why this follow-up is not simply “we found more cases.” The first article explained <a href="https://www.gendigital.com/blog/insights/research/reservation-hijack-scam">how Reservation Hijack scams work</a>. This one shows how far the model has spread.&nbsp;</p><h3>A worldwide footprint, led by Europe&nbsp;</h3><p>The highest number of compromised accommodations in our dataset were linked to <strong>Germany</strong>, followed by <strong>France</strong>, the <strong>United Kingdom</strong>, <strong>Italy</strong>, <strong>Spain</strong>, and the <strong>United States</strong>.&nbsp;</p><p>Germany accounted for 49 compromised accommodations in the dataset. France followed with 35, the United Kingdom with 31, Italy with 24, Spain with 20, and the United States with 19.&nbsp;</p><p>Together, the top five European countries, Germany, France, the United Kingdom, Italy, and Spain, accounted for <strong>159 compromised accommodations</strong>, about <strong>45%</strong> of the full dataset.&nbsp;</p>

<p>The European concentration makes sense. Europe has a dense travel market, a high volume of cross-border bookings, many independent and mid-sized accommodation providers, and a strong dependency on online booking platforms and pre-arrival guest messaging.&nbsp;</p><p>Those conditions give criminals useful cover. Travelers expect messages before arrival. They expect payment questions, check-in instructions, policy reminders, and booking updates. A well-timed fake message does not feel unusual.&nbsp;</p><p>But the country distribution also shows that this is not a single-region problem. The activity spreads across <strong>50 countries</strong>, with a long tail of destinations beyond the largest clusters.&nbsp;</p>

<p>That long tail matters. It suggests the model is not limited to a few obvious tourist destinations or a handful of famous hotel brands. Once criminals have access to reservation data and a working scam flow, the same approach can be adapted to different countries, languages, property types, and booking habits.&nbsp;</p><p>The property does not need to be famous. It only needs to be real, tied to a real reservation, and recognizable to the victim.&nbsp;</p><h3>Not just hotels&nbsp;</h3><p>Hotels make up the largest share of the dataset, but they are not the whole story.&nbsp;</p><p>We identified compromised accommodations across several property types: hotels, aparthotels, apartments, inns, motels, lodges, resorts, guesthouses, B&amp;Bs, hostels, villas, bungalows, and capsule hotels.&nbsp;</p>

<p>This is a useful reminder of how fragmented the travel ecosystem really is. A traveler may book a large hotel chain, a family-run guesthouse, a serviced apartment, a hostel, or a villa through similar platforms and messaging flows.&nbsp;</p><p>From the traveler’s point of view, the trust model is almost the same. They made a booking. They expect communication. They may not know whether the message came from the property, the platform, a channel manager, a property management system, or a compromised account sitting somewhere in between.&nbsp;</p><p>That is exactly the gap criminals are abusing.&nbsp;</p><h3>How big could this problem be?&nbsp;</h3><p>To understand the potential scale of Reservation Hijack scams, we looked at the accommodation properties appearing in our research dataset.&nbsp;</p><p>In total, we identified <strong>350 accommodation entries</strong> linked to reservation hijack scam activity. These were not all the same kind of business. The dataset included hotels, aparthotels, resorts, hostels, guesthouses, villas, apartments and other accommodation types. For each one, we estimated the number of rooms, units, beds or capsules, depending on the property type, and used that to calculate the likely maximum guest capacity.&nbsp;</p><p>Across the deduplicated dataset, these properties represented an estimated maximum capacity of around <strong>82,000 guests at any given time</strong>. Using a conservative occupancy rate of <strong>50%</strong> and an average length of stay of <strong>2.5 nights</strong>, this translates into approximately <strong>6 million guest stays per year</strong>.&nbsp;</p><p>That does not mean 6 million people were scammed. It does not mean 6 million people had their data exposed. What it shows is the size of the opportunity criminals may be looking at when they compromise accommodation or booking communication channels.&nbsp;</p><p>A single compromised workflow can give scammers something much more valuable than a random phone number or email address. It can give them context: the name of the accommodation, the dates of the stay, the booking amount, the channel the guest expects to be contacted through, and the right moment to create urgency.&nbsp;</p><p>That is why Reservation Hijack scams are so convincing. The scam does not feel like spam. It feels like part of the trip.&nbsp;</p>

<h3>The activity does not look random&nbsp;</h3><p>We are still investigating the infrastructure behind these attacks, so we are not attributing the activity to a named group.&nbsp;</p><p>But the evidence does not look like hundreds of unrelated actors randomly copying one another.&nbsp;</p><p>Across the dataset we analyzed, the same fingerprints kept appearing. Many pages used the same internal paths for scripts, images and styles. Several included the same unusual overlay component, repeated internal asset paths, and the same card-validation language, including claims that funds would be reserved and refunded within 10 minutes.&nbsp;</p><p>The pages were also built to look specific to the victim. Hotel names appeared in page titles and visible content. Prices varied from one case to another. Check-in and check-out dates were inserted into the page. In some cases, page metadata and images were synchronized with the accommodation being impersonated. The evidence points to a repeatable process for turning reservation context into property-specific phishing pages. Taken together, those patterns are consistent with a phishing kit designed to generate accommodation-specific pages at scale, rather than pages built manually for each victim.&nbsp;</p><p>The phishing pages also included a fake live support chat. To the victim, it looked like part of the booking or payment process, but it was controlled from the phishing infrastructure. The payment step could therefore become a live interaction: someone behind the page could react to the victim’s input, ask for another card, explain away a failed “validation”, push the victim to continue, or try to capture a one-time code while the victim still believed they were talking to booking support.&nbsp;</p><p>Some of the infrastructure also uses legitimate internet services, including services such as Cloudflare, to place a layer between the visible scam page and the systems behind it. That does not make those services malicious. It means criminals are abusing the same infrastructure that normal websites use, including protective layers that can obscure hosting details, traffic paths, and backend systems.&nbsp;</p><p>For investigators, this kind of setup makes the infrastructure harder to trace. For travelers, it removes many of the usual warning signs. They see a page that loads normally, shows the right accommodation, includes a support chat, and refers to the trip they actually booked. At that point, many people will treat the request as part of the reservation process, even when it is not.&nbsp;</p><h3>Correct information is not proof of legitimacy&nbsp;</h3><p>For years, people have been told to watch for bad spelling, odd sender names, generic greetings, and suspicious links. That advice still helps, but it does not solve this problem.&nbsp;</p><p>A message can include the right accommodation, the right destination, and details from a real stay, and still be malicious. A page can show the correct hotel name, dates, and a plausible payment amount, and still be fake. A request can arrive at the moment when a traveler expects a check-in or payment message, and still be fraud.&nbsp;</p><p>Page behavior can create false confidence too. In some of the phishing pages we analyzed, the fake support chat looked like part of the booking or payment process. If the victim had a question, or if the card “validation” failed, the page could keep the interaction going instead of simply collecting data and stopping there.&nbsp;</p><p>That is what makes Reservation Hijack scams difficult for travelers to judge. The victim is not being tricked only by a fake brand or a fake website. They are being pushed through a process built around real context, at the moment when that context feels normal.&nbsp;</p><p>Travelers expect hotels and booking platforms to contact them. They expect last-minute requests, check-in instructions, payment checks, ID forms, and confirmation messages. Criminals are not fighting that expectation. They are using it.&nbsp;</p><h3>What travelers should do&nbsp;</h3><p>The safest rule is simple: <strong>do not treat correct booking information as proof that a message is legitimate.</strong>&nbsp;</p><p>If a message asks you to verify payment details, confirm a reservation, re-enter card information, pay a balance, reset a PIN, or avoid cancellation, do not use the <a href="https://us.norton.com/blog/online-scams/i-clicked-on-a-phishing-link" target="_blank">link in the message</a>.&nbsp;</p><p>Open the booking platform or hotel app directly. Go to the official website yourself. Use contact details from the original booking confirmation. If needed, call the property using a verified number. Check whether the same request appears inside your official booking account.&nbsp;</p><p>This applies even if the message mentions the right hotel, the right destination, or details from your stay.&nbsp;</p><p>Booking.com has told customers that it will not ask guests to share credit card details by email, phone, WhatsApp, or text, or ask for a bank transfer that differs from the payment policy in the booking confirmation.&nbsp;</p><p>If you already entered payment details into a suspicious page, contact your bank immediately, freeze or cancel the card, and monitor for follow-on fraud. Criminals may reuse the card data later, or sell it to others.&nbsp;</p><h3>What accommodations should take from this&nbsp;</h3><p>For hotels and other accommodation providers, this is not only a guest-awareness issue. Guest communication has become part of the attack surface.&nbsp;</p><p>The systems and workflows between the property and the guest are now valuable targets. That can include hotel staff accounts, booking platform partner accounts, email inboxes, property management systems, guest messaging tools, channel managers, and third-party service providers.&nbsp;</p><p>The lures we have seen on the accommodation side are not exotic. They look like normal hotel work. Some impersonate Booking.com and claim there is a guest complaint waiting for a response. Others say that a paid reservation needs urgent verification, or that the property’s visibility or ranking may be affected if staff do not act quickly. We have also seen payment and invoice-themed messages designed to make staff open attachments or documents that can lead to credential theft or <a href="https://us.norton.com/blog/malware/signs-of-malware" target="_blank">malware infection</a>.&nbsp;</p>

<p>That is why the first visible sign of a Reservation Hijack scam may not be the message sent to the guest. It may start earlier, with an email to a shared hotel inbox, a fake partner-support notice, a malicious attachment, or a document that looks like part of normal accounting or reservation handling. Once reservation context is obtained, whether directly or through another actor in the criminal ecosystem, it can be used later to make guest-facing scams much more convincing.&nbsp;</p><p>For accommodation providers, staff training needs to cover the workflows criminals are actually abusing. Urgent complaints, reservation-verification requests, payment advice emails, invoice notifications, security-update prompts, and any message asking staff to open an attachment, enable content, sign in again, or act under time pressure should all be treated as possible entry points into the same fraud chain.&nbsp;</p><p>The defensive work starts with account protection, but it should not stop there. Accommodation providers need strong <a href="https://us.norton.com/blog/account-safety/multi-factor-authentication" target="_blank">multi-factor authentication</a>, tight control over who can access guest data, monitoring for unusual logins or message patterns, and a clear process for responding when an account may have been abused. The devices used to manage reservations, guest messages, invoices and payment-related emails should also be protected with reliable security protection. Some of the lures we observed were designed to make staff open attachments or documents that could install malware or steal credentials. In those cases, <a href="https://us.norton.com/antivirus" target="_blank">antivirus</a> or endpoint protection may be the last barrier before a compromised inbox becomes a compromised booking workflow.&nbsp;</p><p>Payment-related communication deserves special attention. If a guest receives a payment or verification request, there should be a reliable way to confirm whether it is real. If an account is suspected of being compromised, guests need to be warned quickly and clearly.&nbsp;</p><p>The reputational damage can be painful. Even when the property is also a victim, the traveler may remember the incident as “the hotel message that stole my card details.” That makes workflow security part of customer trust.&nbsp;</p><h3>What the wider travel ecosystem should learn&nbsp;</h3><p>Reservation Hijack scams sit between several parts of the travel industry. The booking platform may see unusual partner activity. The hotel may see confused guests. The traveler sees a convincing message. The bank sees card fraud. A security company sees the landing page.&nbsp;</p><p>Each view is partial, and that delay helps the scam continue.&nbsp;</p><p>The useful signals are often scattered: unusual partner logins, repeated payment-verification language, guest-message spikes, reused templates, fake landing pages, redirects, and infrastructure overlaps. Sharing those signals faster would make it easier to see when separate complaints are really part of the same operation.&nbsp;</p><p>One compromised accommodation can look like a local incident. Hundreds of compromised accommodations across 50 countries point to a repeatable abuse model.&nbsp;</p><h3>The next phase of travel fraud&nbsp;</h3><p>Reservation Hijack scams exploit a simple mistake in how we judge trust online.&nbsp;</p><p>Travelers think: “This message knows my booking, so it must be real.”&nbsp;</p><p>Criminals know: “If we have the booking context, the victim will do much of the trust work for us.”&nbsp;</p><p>The message does not have to be perfect. The website does not have to be flawless. The attacker does not need to convince the victim from zero. They only need to appear inside a relationship that already exists.&nbsp;</p><p>Our latest data shows that this model has spread well beyond isolated cases. We identified <strong>350 compromised accommodations across 50 countries</strong>, covering hotels, apartments, hostels, resorts, guesthouses, villas, and other accommodation types. Together, those properties represent a large travel footprint and millions of estimated annual guest interactions.&nbsp;</p><p>The investigation is still ongoing. We are continuing to analyze infrastructure, campaign overlaps, and the clues suggesting connected activity behind parts of the operation.&nbsp;</p><p>For travelers, the lesson is simple.&nbsp;</p><p>Trust your booking. Do not automatically trust the message.&nbsp;</p>

After our first report, Booking.com began warning customers that reservation data had been accessed. Our continuing investigation shows how criminals are using that data at scale. 

When Hotel Scams Know Your Booking: 350 Compromised Accommodations Across 50 Countries 

Threat Research Team

<p>Attackers replaced selected official download links with malicious installers that deployed a Python bot, r77 rootkit components, and Windows policy-based defense evasion.</p><p>On May 6, 2026, attackers compromised the official JDownloader website and swapped download links to serve trojanized installers. The JDownloader developers <a href="https://www.reddit.com/r/jdownloader/comments/1t6goqe/is_the_website_hacked/">confirmed the breach</a> within hours, restored clean files, and disclosed a timeline, but acknowledged they didn't know what the malicious installers actually do. We took the malware apart to answer that question.</p><p>&nbsp;</p><p>What we found goes well beyond a typical trojanized installer. The payload is a multi-component attack framework: a Python bot protected by PyArmor v9, an r77 rootkit stager with AMSI bypass, and a Windows Defender Application Control (WDAC) policy that blocks 50 security executables from running, including Avast, AVG, Avira, Windows Defender, HitmanPro, and Kaspersky Virus Removal Tool. We reversed the full C2 protocol from the obfuscated Python bytecode and recovered the campaign configuration from the dropper's encrypted strings.</p><p>&nbsp;</p><h2>The infection chain</h2><p>The trojanized installer is unsigned. Windows SmartScreen blocks it, and users who ran it had to manually bypass the warning. Inside, it wraps the legitimate JDownloader installer alongside an XOR-encrypted second-stage PE:</p>

<p>Stage 2 acts as the campaign's quartermaster. It deploys five components from XOR-encrypted resources embedded in its PE (key: <code>fywo</code>):</p><table class="table"><thead><tr><th>Component</th><th>Purpose</th></tr></thead><tbody><tr><td><strong>PyArmor bot</strong></td><td>The main payload, a Python script with obfuscated bytecode</td></tr><tr><td><strong>PyArmor runtime</strong></td><td>DLL that decrypts the bot's bytecode at execution time</td></tr><tr><td><strong>r77 rootkit stager</strong></td><td>Native x86 PE that hides the bot's process, files, and registry keys</td></tr><tr><td><strong>WDAC Code Integrity policy</strong></td><td>Blocks 50 AV/EDR executables from running after reboot</td></tr><tr><td><strong>Python 3.14.3 installer</strong></td><td>The legitimate Python runtime (needed to run the bot)</td></tr></tbody></table><p>Before doing any of this, Stage 2 calls <code>WaitForSingleObject</code> with a 300-second timeout — three times in sequence. This 5-minute-per-call delay is designed to outlast automated sandboxes, which typically give samples 2-5 minutes of execution time. One sandbox vendor recorded an 8-minute total wait before any malicious behavior appeared.</p><p>&nbsp;</p><h2>Killing your antivirus before it can fight back</h2><p>The most operationally significant component is the WDAC Code Integrity policy.</p><p>Windows Defender Application Control (WDAC) policies tell the operating system which executables are allowed to run. The attackers deploy a deny-list policy to <code>%WINDIR%\System32\CodeIntegrity\SIPolicy.p7b</code> that blocks 50 executable paths across six security vendors plus core Windows security services:</p><table class="table"><thead><tr><th>Target</th><th>Blocked executables</th></tr></thead><tbody><tr><td><strong>Avast</strong></td><td>AvastSvc.exe, AvastUI.exe, afwServ.exe, aswEngSrv.exe, aswidsagent.exe, aswToolsSvc.exe, wsc_proxy.exe, Icarus components, Overseer</td></tr><tr><td><strong>AVG</strong></td><td>All executables under Program Files\AVG\Antivirus</td></tr><tr><td><strong>Avira</strong></td><td>Security, VPN, Fallback Updater, Optimizer Host, Endpoint Protection SDK</td></tr><tr><td><strong>Windows Defender</strong></td><td>MsMpEng.exe, MpCmdRun.exe, MpDefenderCoreService.exe</td></tr><tr><td><strong>Windows Security</strong></td><td>SecurityHealthHost.exe, SecurityHealthService.exe, SecurityHealthSystray.exe</td></tr><tr><td><strong>Windows Update</strong></td><td>MoUsoCoreWorker.exe, wuauclt.exe, wusa.exe</td></tr><tr><td><strong>Others</strong></td><td>HitmanPro, Kaspersky Virus Removal Tool, Farbar Recovery Scan Tool</td></tr></tbody></table><p>After the next reboot, none of these executables can start. The AV service is effectively dead. It won't run, it can't scan, and Windows Update can't push signature updates. One victim in the Reddit thread reported that Windows Defender disappeared entirely after running the trojanized installer.</p><p>This is a known but uncommon TTP (MITRE T1562.001). It requires the installer to run elevated, which the SmartScreen bypass dialog would have prompted for. Users who clicked through both warnings — SmartScreen and UAC — gave the malware everything it needed.</p><h2>&nbsp;</h2><h2>How the dropper provisions the bot</h2><p>Stage 2's strings are all XOR-obfuscated with the same <code>fywo</code> key used for its resources. After deobfuscation, we recovered 122 strings including registry paths, API names, and encrypted configuration values.</p><p>The dropper writes the bot's initial configuration to <code>HKCU\SOFTWARE\Python</code>. Both the registry value names and data are RC4-encrypted and hex-encoded — making the registry entries look like random hex strings to casual inspection. We recovered two configuration values:</p><ul><li data-list-item-id="e15e9100cccadef17d91598e244b0b038"><strong>CampaignID</strong> a unique identifier for this campaign, used during bot registration with the C2 server.</li><li data-list-item-id="e7a2666057614636498fba93e483028cf"><strong>DDRList</strong> six dead-drop resolver URLs that the bot uses to discover its C2 servers (detailed in the next section).</li></ul><p>Notably, the dropper does not write a C2 server list directly. The bot discovers its command-and-control addresses exclusively through the dead-drop resolver mechanism — a design choice that makes the infrastructure resilient to takedowns.</p><p>&nbsp;</p><h2>Dead-drop resolvers: how the bot finds its C2</h2><p>A dead-drop resolver (DDR) is an intermediary, a legitimate web page where the operator publishes encrypted C2 addresses. The bot fetches the page, extracts and decrypts the content, and connects to whatever C2 servers it finds. If the operator needs to rotate infrastructure, they update the DDR page and every infected machine follows automatically.</p><p>The bot reads its DDR list from the registry, fetches each URL, and RC4-decrypts the page content. Valid payloads start with the prefix <code>VAL:</code> followed by a semicolon-separated list of C2 URLs.</p><p>We extracted all six dead-drop resolver URLs from the dropper and probed them:</p><table class="table"><thead><tr><th>URL</th><th>Status</th><th>Decrypted content</th></tr></thead><tbody><tr><td><code>telegra[.]ph/tr02-05-02</code></td><td>Live</td><td>C2 list: parkspringshotel[.]com + auraguest[.]lk</td></tr><tr><td><code>telegra[.]ph/ki06-05-02</code></td><td>Live</td><td><code>VAL:XX</code> — placeholder for future C2 rotation</td></tr><tr><td><code>rentry[.]co/zzk7opdu</code></td><td>Live</td><td>Same C2 list</td></tr><tr><td><code>rentry[.]org/wayc2qqz</code></td><td>Live</td><td><code>VAL:XX</code> — placeholder</td></tr><tr><td><code>codeberg[.]org/etienne74/guix/...</code></td><td>404</td><td>Removed or never created</td></tr><tr><td>`2wxjoz6lkdxkniksujbdknkugweemx7uvxdr4ejgyipce4tnvktvbvqd.onion/t`</td><td>Not probed</td><td>Tor hidden service DDR</td></tr></tbody></table><p>The operator has two live C2 servers and four reserve dead-drop pages — two stubs ready for C2 rotation and one Tor fallback. If the current C2 infrastructure gets burned, the operator updates a Telegraph or Rentry page and every infected machine picks up the new address on its next poll cycle.</p><p>Beyond the dead-drop mechanism, the bot has a domain generation algorithm (DGA) as a last-resort fallback. It combines four seeds (<code>XNerWs4I</code>, <code>e55gegnW</code>, <code>RjWN0Y9m</code>, <code>AemOU1co</code>) with 14 TLDs and an ISO-week-based rotation to produce 56 candidate domains per week. We probed all current DGA domains — none are registered. The operator is running purely on dead-drop infrastructure for now, but the DGA ensures the botnet can survive even if all resolver pages and C2 servers are taken down simultaneously.</p><p>&nbsp;</p><h2>The C2 protocol: RSA-OAEP wrapping AES-GCM</h2><p>We reversed the bot's full communication protocol from the PyArmor-protected bytecode. It uses a layered encryption scheme designed to prevent passive interception and session tampering:</p>

<p>The bot wraps a fresh AES-256 key with the hardcoded RSA-2048 public key (OAEP, SHA-256) and sends it to the C2. The server proves possession of the private key by returning <code>"ok"</code> encrypted with AES-GCM. From that point, every message in both directions is AES-256-GCM encrypted with a per-direction sequence counter as authenticated associated data — preventing replay and reordering.</p><p>After the handshake, the bot registers with the campaign ID provisioned by the dropper. The server returns a <code>bot_id</code> and <code>bot_pass</code> that the bot stores in the registry for subsequent polling. The bot's primary capability is arbitrary Python code execution — the attacker can ship any Python code and the bot will run it and return the output.</p><p>All identified C2 and staging servers are compromised <a href="https://qloapps.com/">QloApps</a> hotel reservation websites:</p><table class="table"><thead><tr><th>Domain</th><th>Role</th><th>IP</th><th>PHP</th><th>Location</th></tr></thead><tbody><tr><td><code>parkspringshotel[.]com</code></td><td>C2 panel</td><td>172.96.172[.]91</td><td>8.3.30</td><td>Ghana</td></tr><tr><td><code>auraguest[.]lk</code></td><td>C2 panel</td><td>209.133.215[.]178</td><td>8.3.30</td><td>Sri Lanka</td></tr><tr><td><code>checkinnhotels[.]com</code></td><td>Linux payload staging</td><td>66.29.137[.]25</td><td>7.4.33</td><td>—</td></tr></tbody></table><p>The two C2 servers share identical JARM fingerprints and run the same PHP version, confirming the same C2 panel software is deployed on both. The third domain, <code>checkinnhotels[.]com</code>, was used to host the Linux payload disguised as an SVG file (<a href="https://www.bleepingcomputer.com/news/security/jdownloader-site-hacked-to-replace-installers-with-python-rat-malware/">BleepingComputer</a>). All three run QloApps — an open-source hotel booking CMS — suggesting the attacker specifically targets this software to build their infrastructure. None of the domains had malicious detections on VirusTotal at the time of discovery. We confirmed both C2 servers remain operationally live as of May 11.</p><h2>&nbsp;</h2><h2>The r77 rootkit stager</h2><p>The rootkit stager is a 176 KB native x86 PE based on the open-source <a href="https://github.com/bytecode77/r77-rootkit">r77 rootkit</a>. It contains an embedded .NET assembly that performs four operations:</p><ol><li data-list-item-id="e9ca3772c2bd6052d86931268e23d036a"><strong>AMSI bypass</strong> — a PowerShell cradle patches <code>AmsiScanBuffer</code> in memory, disabling Windows' Antimalware Scan Interface before any script payload runs.</li><li data-list-item-id="e01c27cd4c721b2dabe18b819d05c84fe"><strong>Reflective DLL injection</strong> — injects the r77 hooking DLLs (32-bit and 64-bit variants) into <code>winlogon.exe</code>. These DLLs hook Windows API functions to hide any process, file, or registry key whose name starts with the <code>$77</code> prefix.</li><li data-list-item-id="e254d7da7ebd6dfd7d57f7c5f67760ba3"><strong>Registry persistence</strong> — stores the stager assembly as a binary blob in <code>HKLM\SOFTWARE\$77stager</code> and reloads it at every boot via .NET reflection.</li><li data-list-item-id="ef200c38559748bd535edaf6a0d5aa3d5"><strong>Service creation</strong> — installs a Windows service (<code>$77svc</code>) to ensure the rootkit survives reboots independently of the registry mechanism.</li></ol><p>Once r77 is active, the <code>$77</code> prefix acts as an invisibility cloak. The Python bot calls <code>r77_hide_self()</code> and <code>r77_hide_registry_path()</code> to rename its own process and registry hive with this prefix, making them invisible to Task Manager, <code>regedit</code>, and most security tools.</p><h2>&nbsp;</h2><h2>The Python bot under PyArmor v9</h2><p>The final payload is a Python script protected by <a href="https://pyarmor.dashingsoft.com/">PyArmor</a> v9, a commercial bytecode obfuscation tool. PyArmor encrypts each function's bytecode individually and decrypts it at runtime through a native DLL — making static analysis significantly harder than standard Python malware.</p><p>We built a custom tool to decrypt and disassemble the protected bytecode, recovering 30 functions totaling 7,326 lines of disassembly. The bot is cross-platform (Windows and Linux), uses gevent for asynchronous I/O, and handles the full lifecycle: configuration management, C2 discovery via dead-drop resolvers and DGA, encrypted communication, task execution, and rootkit integration.</p><p>The bot's primary capability is executing arbitrary Python code received from the C2 server. Combined with the Python 3.14 runtime installed by the dropper, this gives the operator the ability to deploy any follow-on payload — keyloggers, credential stealers, lateral movement tools — without needing to push new binaries to the victim.</p><h2>&nbsp;</h2><h2>Impact and recommendations</h2><p>Users who downloaded JDownloader from the official website between May 6 and May 7, 2026, using the "Download Alternative Installer" links (Windows) or the Linux shell installer link are potentially compromised. The <a href="https://jdownloader.org/incident_8.5.2026.html">official incident report</a> lists eight malicious installer hashes across x86/amd64 and multiple JRE versions. The attackers exploited an unpatched CMS vulnerability to swap download links — the actual installer files hosted externally were never modified. In-app updates, macOS downloads, and package manager installs (Flatpak, Winget, Snap) were not affected.</p><p>The Linux attack chain, [first reported by BleepingComputer](https://www.bleepingcomputer.com/news/security/jdownloader-site-hacked-to-replace-installers-with-python-rat-malware/), follows a different delivery path. We downloaded the trojanized shell installer and its payload to verify the claims and dig deeper.d. The modified install4j script requires root, checks for x86_64 architecture, and downloads a 20 MB tar.gz from <code>checkinnhotels[.]com/img/logo1.svg</code> (disguised with <code>Content-Type: image/svg+xml</code> — still live as of May 11). The archive contains two files: a 3 KB SUID-root helper (<code>systemd-exec</code>) and a 21 MB PyInstaller bundle (<code>pkg</code>). The helper is a minimal ELF that calls <code>setuid(0)</code>, <code>setgid(0)</code>, and <code>execvp()</code> — installed to <code>/usr/bin/systemd-exec</code> with <code>chmod 4755</code>. Persistence is created via <code>/etc/profile.d/systemd.sh</code>, which launches the payload masquerading as <code>/usr/libexec/upowerd</code>.</p><p>We decrypted the PyArmor-protected Python bytecode from the Linux payload and confirmed it is <strong>the same bot source code</strong> as the Windows variant — identical RSA public key, DGA seeds, RC4 keys, C2 protocol, and DDR handler logic. The same campaign ID (<code>NdcHsJPM</code>) and all six DDR URLs are written to <code>~/.local/share/</code> as RC4-encrypted files (mirroring the Windows registry approach). The only difference is the Python runtime: the Linux bundle uses Python 3.12 (packaged via PyInstaller) versus Python 3.14 on Windows.</p><p>The JDownloader developers restored clean downloads on May 9 and published a detailed incident timeline. Users who already had JDownloader installed and received updates through the application's built-in updater were not affected — only fresh downloads from the website during the compromise window were trojanized.</p><p><strong>If you ran the trojanized installer:</strong></p><ul><li data-list-item-id="e78c8637f87f47adb2a6c0e9e37ff1466">The WDAC policy may have disabled your antivirus. Check <code>%WINDIR%\System32\CodeIntegrity\SIPolicy.p7b</code> — if it exists and you didn't create it, delete it and reboot.</li><li data-list-item-id="e5a9344602452a9e77dfe81e30c45fd8c">The registry keys <code>HKCU\SOFTWARE\Python</code> (bot config) and <code>HKLM\SOFTWARE\$77stager</code> (rootkit) are strong indicators of compromise — but if r77 is active, its API hooks hide all <code>$77</code>-prefixed registry keys and the bot's own hive from standard tools like <code>regedit</code>. To inspect these, boot from a Windows recovery environment or mount the registry hives offline.</li><li data-list-item-id="edcbc2f271c7b2885893f8f995fe252eb">A clean OS reinstall is the safest remediation. The r77 rootkit's reflective injection into <code>winlogon.exe</code> and AMSI bypass make partial cleanup unreliable.</li></ul><p><strong>For defenders:</strong></p><ul><li data-list-item-id="efcd7ce434d65f159da0dbff097d5fb44">The bot uses the default Python User-Agent <code>Python-urllib/3.14</code>. While not unique on its own, it can help correlate connections to the C2 URLs and DDR pages listed below.</li><li data-list-item-id="e35fe4757c01a79131defbd71e6762bfb">Monitor for DNS queries to the DGA pattern: 15-character lowercase alphanumeric hostnames on TLDs including <code>.top</code>, <code>.cfd</code>, <code>.sbs</code>, <code>.cyou</code>, <code>.icu</code>, <code>.casa</code>.</li><li data-list-item-id="e41ab2df0dd210b9e338012701bdf4398">The mutex name <code>Global\0C3C1D37</code> can serve as a host-based indicator.</li><li data-list-item-id="e68e99d7961368cd02568989f8e767d08">Block the dead-drop resolver pages: <code>telegra[.]ph/tr02-05-02</code>, <code>telegra[.]ph/ki06-05-02</code>, <code>rentry[.]co/zzk7opdu</code>, <code>rentry[.]org/wayc2qqz</code>.</li></ul><h2>&nbsp;</h2><h2>Indicators of Compromise</h2><p>Full IOC list available on <a href="https://github.com/avast/ioc">GitHub</a>.</p><h3>Hashes (SHA-256)</h3><table class="table"><thead><tr><th>Artifact</th><th>Hash</th></tr></thead><tbody><tr><td>Stage 1 — Windows (analyzed variant)</td><td><code>5a6636ce490789d7f26aaa86e50bd65c7330f8e6a7c32418740c1d009fb12ef3</code></td></tr><tr><td>Stage 1 — Linux shell installer</td><td><code>6d975c05ef7a164707fa359284a31bfe0b1681fe0319819cb9e2c4eec2a1a8af</code></td></tr><tr><td>Stage 2 (C++ dropper)</td><td><code>77a60b5c443f011dc67ace877f5b2ad7773501f3d82481db7f4a5238cf895f80</code></td></tr><tr><td>Stage 3 — Windows (PyArmor bot)</td><td><code>5fdbee7aa7ba6a5026855a35a9fe075967341017d3cb932e736a12dd00ed590a</code></td></tr><tr><td>PyArmor runtime DLL</td><td><code>33318499489cdb82543c0bfea699b98f5928c7a360966df6e958a9cbc2eab3fe</code></td></tr><tr><td>r77 rootkit stager</td><td><code>5c887054cb1dce077943afa955db43306f66795f7cbda8233d8ba25230a23d41</code></td></tr><tr><td>WDAC CI policy</td><td><code>5ee86c177dc5bdba05e3bdc67b07115c66097f825fff257bf0d4a999bbb8a1ea</code></td></tr><tr><td>Linux payload archive (logo1.svg)</td><td><code>6550672cac21e036882921dd934ee06552dc74d3b0a9e1ddc26f952855e11371</code></td></tr><tr><td>Linux SUID helper (systemd-exec)</td><td><code>25744e90bfa44cbcbf1f3d3c3cb90dd79dd32a6e359df9d2660ff251d6d03b46</code></td></tr><tr><td>Linux PyInstaller bot (pkg)</td><td><code>bf47585bd0b39f0731f044b37a95eb7e311ad31b23b50306a113a3aa777dbfab</code></td></tr></tbody></table><p>Six additional Windows installer variants are listed in the <a href="https://jdownloader.org/incident_8.5.2026.html">official incident report</a>. Full hash list on <a href="https://github.com/avast/ioc/tree/master/JDownloaderRAT">GitHub</a>.</p><h3>Network indicators</h3><table class="table"><thead><tr><th>Type</th><th>Value</th><th>Context</th></tr></thead><tbody><tr><td>C2 URL</td><td><code>parkspringshotel[.]com/m/Lu6aeloo.php</code></td><td>Active C2</td></tr><tr><td>C2 URL</td><td><code>auraguest[.]lk/m/douV2quu.php</code></td><td>Active C2</td></tr><tr><td>Staging</td><td><code>checkinnhotels[.]com/img/logo1.svg</code></td><td>Linux payload (still live)</td></tr><tr><td>C2 IP</td><td><code>172.96.172[.]91</code></td><td>parkspringshotel.com</td></tr><tr><td>C2 IP</td><td><code>209.133.215[.]178</code></td><td>auraguest[.]lk</td></tr><tr><td>Staging IP</td><td><code>66.29.137[.]25</code></td><td>checkinnhotels.com</td></tr><tr><td>Dead-drop resolver</td><td><code>telegra[.]ph/tr02-05-02</code></td><td>Live, serves encrypted C2 list</td></tr><tr><td>Dead-drop resolver</td><td><code>rentry[.]co/zzk7opdu</code></td><td>Live, serves encrypted C2 list</td></tr><tr><td>Dead-drop resolver</td><td><code>telegra[.]ph/ki06-05-02</code></td><td>Stub, reserved for C2 rotation</td></tr><tr><td>Dead-drop resolver</td><td><code>rentry[.]org/wayc2qqz</code></td><td>Stub, reserved for C2 rotation</td></tr></tbody></table><h3>Host indicators</h3><table class="table"><thead><tr><th>Type</th><th>Value</th></tr></thead><tbody><tr><td>Mutex</td><td><code>Global\0C3C1D37</code></td></tr><tr><td>Registry (bot config)</td><td><code>HKCU\SOFTWARE\Python\*</code> (hex-encoded RC4-encrypted value names)</td></tr><tr><td>Registry (r77)</td><td><code>HKLM\SOFTWARE\$77stager</code>, <code>$77dll32</code>, <code>$77dll64</code>, <code>$77svc</code></td></tr><tr><td>WDAC policy</td><td><code>%WINDIR%\System32\CodeIntegrity\SIPolicy.p7b</code> (GUID <code>{31351756-3F24-4963-8380-4E7602335AAE}</code>)</td></tr><tr><td>Bot process</td><td><code>pythonw.exe</code> (Python 3.14, User-Agent <code>Python-urllib/3.14</code>)</td></tr><tr><td>Tor drop path</td><td><code>C:\ProgramData\tor\tor\tor.exe</code></td></tr><tr><td>Linux SUID binary</td><td><code>/usr/bin/systemd-exec</code></td></tr><tr><td>Linux payload</td><td><code>/root/.local/share/.pkg</code></td></tr><tr><td>Linux persistence</td><td><code>/etc/profile.d/systemd.sh</code></td></tr><tr><td>Linux masquerade</td><td><code>/usr/libexec/upowerd</code></td></tr></tbody></table><h3>MITRE ATT&amp;CK</h3><table class="table"><thead><tr><th>Technique</th><th>ID</th></tr></thead><tbody><tr><td>Supply Chain Compromise: Compromise Software Supply Chain</td><td>T1195.002</td></tr><tr><td>Obfuscated Files or Information</td><td>T1027</td></tr><tr><td>Impair Defenses: Disable or Modify Tools</td><td>T1562.001</td></tr><tr><td>Process Injection: Dynamic-link Library Injection</td><td>T1055.001</td></tr><tr><td>Web Service: Dead Drop Resolver</td><td>T1102.001</td></tr><tr><td>Dynamic Resolution: Domain Generation Algorithms</td><td>T1568.002</td></tr><tr><td>Encrypted Channel: Asymmetric Cryptography</td><td>T1573.002</td></tr><tr><td>Rootkit</td><td>T1014</td></tr><tr><td>Create or Modify System Process: Windows Service</td><td>T1543.003</td></tr><tr><td>Modify Registry</td><td>T1112</td></tr></tbody></table><p>For customers using Norton, Avast, AVG, Avira or any other security product, the most important question is whether the malicious installer was executed. If you downloaded an affected installer but did not run it, delete the file, download a fresh installer from the official JDownloader site, and run a full scan with up-to-date protection. If you ran the installer, or cannot rule out that you ran it, treat the system as compromised. JDownloader recommends a clean operating system reinstall in this situation, and we agree that this is the safest baseline. The Windows payload includes rootkit behavior, persistence, encrypted configuration and policy-based defense evasion, so a normal scan may reduce risk but cannot guarantee that every persistence mechanism has been removed. Until the system has been rebuilt or inspected from a trusted recovery environment, avoid using it for sensitive activity. Do not log in to email, banking, work accounts, password managers or other important services from that machine. Change important passwords from another trusted device, and monitor accounts for unusual activity.</p><p>&nbsp;</p>

Malware that hid itself on infected systems and disabled antivirus protection.

Inside the JDownloader Supply-Chain Attack: An r77 Rootkit Bot That Kills Your Antivirus

<p><strong>TLDR: </strong>Bedep was a malware family active mainly in 2014 and 2015 that used an unusually sophisticated domain generation algorithm, or DGA, to hide its command-and-control infrastructure. Instead of relying only on the date, it used real foreign exchange rates published by the <em>European Central Bank</em>, making its future domains much harder to predict in advance. Under the hood, the malware used ideas from group theory to generate a fixed set of unique domains without collisions, a rare example of advanced mathematics being applied directly in real-world malware.</p><p>Most domain generation algorithms are boring. A linear congruential generator, a date seed, some modular arithmetic, a character table -- <code>seed = (seed * 0x41C64E6D + 0x3039) % 2^31</code>, rinse, repeat. You reverse them in an afternoon, pre-compute next month's domains over lunch, and move on.</p><p>Bedep author implemented a number theory textbook inside a 32-bit DLL, and the result is one of the most mathematically elegant pieces of malware ever shipped.</p><p>This post is a deep dive into this unique engineering.</p><h2>What is Bedep?</h2><p>Bedep is an ad-fraud botnet that was active from late 2014 through 2015, delivered exclusively through the Angler exploit kit. When a Flash zero-day (CVE-2015-0311) was burning, Angler was dropping Bedep. The malware itself was a modular downloader focused on click fraud, but its infrastructure is what made it interesting. In early 2015, new variants appeared with a DGA for C2 resolution. A three-day sinkhole by Arbor Networks (ASERT) caught phone-homes from roughly 82,000 unique IPs, spread across every continent except -- notably -- Russia.</p><p>Dennis Schwarz originally reversed the DGA at ASERT, who published a proof-of-concept Python reimplementation and a detailed write-up titled <em>"Bedep's DGA: Trading Foreign Exchange for Malware Domains."</em> The original blog post has since been taken down from NETSCOUT's site, but survives on the <a href="https://web.archive.org/web/20160311083109/http://www.arbornetworks.com:80/blog/asert/bedeps-dga-trading-foreign-exchange-for-malware-domains/">Wayback Machine</a>. The PoC lived at <code>github.com/arbor/bedep_dga</code>. Dennis got the algorithm working but noted that parts of it were opaque -- he called the core transform a "blackbox" and flagged the embedded table as "likely something Fermat number related." He was right. Let's open that box.</p><p>&nbsp;</p><h2>The ECB trick: Seeding a DGA from the financial markets</h2><p>Before the math starts, Bedep needs a seed that both the bot and the botmaster can independently derive without communicating. Most DGAs use the date. Bedep uses the date <em>and</em> the global foreign exchange market.</p><p>The algorithm fetches two XML files from legitimate public services:</p><ol><li data-list-item-id="ec5890edf5187711796f804fae7ad8577"><strong>UTC time</strong> from <code>earthtools.org/timezone/0/0</code> -- the current timestamp, converted to "days since year zero."</li><li data-list-item-id="ead6313dc967de96442575ff50339b412"><strong>Euro foreign exchange reference rates</strong> from <code>www.ecb.europa.eu/stats/eurofxref/eurofxref-hist-90d.xml</code> -- the European Central Bank's daily publication of EUR conversion rates against 31+ world currencies, updated every business day.</li></ol><p>The time is used to select which day's rates to use. Specifically, Bedep picks "last Tuesday's" exchange rates -- meaning the preceding week's Tuesday until Thursday, after which it rolls forward to the current week's Tuesday. Only rates falling on a Monday boundary (in the algorithm's day-counting scheme) are considered. This gives a roughly weekly rotation with a deterministic selection rule.</p><p>From the chosen date, Bedep extracts up to 48 currency rates -- USD, JPY, GBP, CZK, BGN, HUF, and so on. Each rate is parsed through a slightly broken custom <code>atof()</code> implementation (off by a bit in the least significant digits -- a quirk, not a feature), packed into a 64-bit IEEE double, and its low 32-bit dword is extracted for use in the algorithm.</p><p>Here is what a single run looks like, from the PoC output for April 7, 2015:</p><p><code>parsed 31 currencies from 2015-04-07 (currency date): &nbsp; &nbsp;USD: 1.0847 &nbsp; &nbsp; &nbsp;JPY: 130.33 &nbsp; &nbsp; BGN: 1.9558 &nbsp; &nbsp;CZK: 27.455 &nbsp; &nbsp; &nbsp;DKK: 7.4714 &nbsp; &nbsp;GBP: 0.7286 &nbsp; &nbsp;HUF: 299.08 &nbsp; &nbsp; &nbsp;PLN: 4.0578 &nbsp; &nbsp;RON: 4.4165 &nbsp; &nbsp;SEK: 9.374 &nbsp; &nbsp; &nbsp; CHF: 1.0438 &nbsp; &nbsp;NOK: 8.73 &nbsp; &nbsp;HRK: 7.619 &nbsp; &nbsp; &nbsp; RUB: 59.8265 &nbsp; TRY: 2.8079 &nbsp; &nbsp;AUD: 1.4192 &nbsp; &nbsp; &nbsp;BRL: 3.3979 &nbsp; &nbsp;CAD: 1.3563 &nbsp; &nbsp;CNY: 6.7241 &nbsp; &nbsp; &nbsp;HKD: 8.4086 &nbsp; &nbsp;IDR: 14091.77 &nbsp; &nbsp;ILS: 4.267 &nbsp; &nbsp; &nbsp; INR: 67.598 &nbsp; &nbsp;KRW: 1183.28 &nbsp; &nbsp;MXN: 16.1919 &nbsp; &nbsp; MYR: 3.9527 &nbsp; &nbsp;NZD: 1.4423 &nbsp; &nbsp;PHP: 48.3 &nbsp; &nbsp; &nbsp; &nbsp;SGD: 1.4724 &nbsp; &nbsp;THB: 35.335 &nbsp; &nbsp;ZAR: 12.8345</code></p><p>&nbsp;</p>

<p>Why is this clever? Because the ECB rates are:</p><ul><li data-list-item-id="e5f3c952abb440c715bcfa626ac9bd4c0"><strong>Publicly available</strong> -- anyone can fetch the same XML</li><li data-list-item-id="e7730a0d72c71be00a0c3d3feebc10618"><strong>Globally consistent</strong> -- every bot on every continent gets the same data</li><li data-list-item-id="e1667d4c4edd48ffbda05118e24153bf0"><strong>Unpredictable in advance</strong> -- nobody can predict next Tuesday's EUR/USD rate</li><li data-list-item-id="e80b9125dab13aae37cb9ed8b88656475"><strong>Historically verifiable</strong> -- the ECB publishes archives going back years</li><li data-list-item-id="e0d9bf0abba3c6cb7703705ce6203f707"><strong>Impossible to tamper with</strong> -- the ECB is not going to modify their reference rates to help you sinkhole a botnet</li></ul><p>And because the malware fetches this from <code>ecb.europa.eu</code>, the request looks like legitimate traffic. A Snort signature (SID 33188) was written to detect it, but it fired constantly on real users checking exchange rates.</p><h2>The mathematical core</h2><p>This is where Bedep stops being a clever botnet and starts being a discrete mathematics exercise.</p><h3>Precomputed subgroup parameters</h3><p>The DLL embeds a lookup table -- 102 entries of 8 dwords each, stored as JSON in the PoC (<code>transform2_table_varN.json</code>, one per config variant). At first glance it looks like random constants. It is not.</p><p>The <code>transform2</code> function takes a hash derived from the exchange rates and days-since value, then uses it as an index into this table. Each table entry, after being decoded through config-specific XOR and multiply constants (<code>0x663d81 * entry[0] ^ value3</code> and <code>0x281 * entry[1] ^ value2</code>), yields two critical values:</p><ul><li data-list-item-id="ee4084ac1a9ee922a9a2585119d02acb9"><strong>p</strong> -- a prime number</li><li data-list-item-id="e7d298adce011a8fe31f7d5db7f1685ee"><strong>q</strong> -- an integer such that q divides p - 1</li></ul><p>This is the subgroup structure. The table stores primes whose group orders (p - 1) have known factorizations with small prime factors. The malware doesn't need to factor p - 1 at runtime -- that hard work was done offline by the author and baked into the DLL. Dennis Schwarz noted these were "likely something Fermat number related," and he was onto something: the primes are chosen so that their totient has a smooth factorization, making generator-finding tractable.</p><p>The number of domains to generate comes directly from q - 1. For the first config, this works out to 22 domains; for the second, 28 -- totaling 50 domains per weekly rotation.</p><h3>Finding generators: A textbook primitive root search</h3><p>With p and the prime factorization of p - 1 in hand, Bedep needs a generator of the multiplicative group ((\mathbb{Z}/p\mathbb{Z})^*) -- or more precisely, of a specific subgroup of order q.</p><p>The <code>transform8</code> function does this in two stages. First, it runs a <strong>trial-division prime sieve</strong>: starting from 3, stepping by 2 (skipping evens), it tests each candidate against all previously found primes. It collects up to 37 small primes, then filters for those that actually divide q (the subgroup order). This gives the prime factorization of q.</p><p>Then <code>transform3</code> finds the <strong>primitive root</strong> itself. This is the standard algorithm straight from a number theory textbook:</p><p><code>def find_primitive_root(p, prime_factors_of_order): &nbsp; &nbsp;for g in range(2, p // 2): &nbsp; &nbsp; &nbsp; &nbsp;is_generator = True &nbsp; &nbsp; &nbsp; &nbsp;for q_i in prime_factors_of_order: &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;# If g^((p-1)/q_i) ≡ 1 (mod p), then g generates &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;# a proper subgroup, not the full group. Reject it. &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;if pow(g, (p - 1) // q_i, p) == 1: &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;is_generator = False &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;break &nbsp; &nbsp; &nbsp; &nbsp;if is_generator: &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;return g &nbsp; &nbsp;return None</code></p>

<p>The actual code in <code>transform3</code> is this logic rendered in C-style loop structure with manual index tracking, but the mathematics is identical. For each candidate g starting from 2, it checks:</p><p>[ g^{(p-1)/q_i} \not\equiv 1 \pmod{p} \quad \text{for all prime factors } q_i \text{ of } p-1 ]</p><p>If g passes all checks, it generates the full group. This is literally the algorithm from Section 11.1 of Shoup's <em>A Computational Introduction to Number Theory and Algebra</em>, implemented in a malware DLL.</p><h3>Walking the cyclic group</h3><p>Now comes the payoff. With a prime p, a generator g, and a subgroup order q, the <code>transform7</code> function sets up the DGA's iteration state:</p><p><code>modulus &nbsp; &nbsp;= p &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;# field_c seed &nbsp; &nbsp; &nbsp; = pow(g, random_e, p) &nbsp; &nbsp; &nbsp; &nbsp;# field_4 -- starting element step &nbsp; &nbsp; &nbsp; = pow(g2, random_f, q) &nbsp; &nbsp; &nbsp; # field_8 -- step exponent</code></p>

<p>The starting position <code>seed</code> is g raised to a random exponent (derived from <code>rdtsc</code>, the CPU timestamp counter). The step is similarly randomized from a second generator. Both are computed via modular exponentiation.</p><p>Then, for each domain, the iteration is simply:</p><p><code>seed = pow(seed, step, modulus) &nbsp; &nbsp; # one step through the cyclic group domain = seed_to_domain(seed, currencies)</code></p>

<p>That single line -- <code>pow(seed, step, modulus)</code> -- is the entire DGA engine. Each call advances the state to the next element of the cyclic subgroup.</p><p>Because the subgroup has order q, and step is coprime to q (guaranteed by the generator construction), this walk visits every non-identity element of the subgroup exactly once before cycling. The number of domains generated equals q - 1, which is precisely the number of non-identity elements. No collisions. No wasted iterations. No off-by-one hoping you hit enough domains.</p><p><strong>The key insight:</strong> the set of group elements visited is deterministic (fixed by p, g, and the exchange rates), but the <em>order</em> of visitation depends on the random exponents from <code>rdtsc</code>. Every infected machine walks through the same set of q - 1 elements, generating the same q - 1 domain names, but potentially in a different order. Same destinations, different paths.</p><p><code>flowchart TB &nbsp; &nbsp;subgraph cyclic_group ["Cyclic Subgroup of (Z/pZ)*"] &nbsp; &nbsp; &nbsp; &nbsp;E1["g^1 mod p"] --&gt; E2["g^2 mod p"] &nbsp; &nbsp; &nbsp; &nbsp;E2 --&gt; E3["g^3 mod p"] &nbsp; &nbsp; &nbsp; &nbsp;E3 --&gt; E4["..."] &nbsp; &nbsp; &nbsp; &nbsp;E4 --&gt; Eq["g^(q-1) mod p"] &nbsp; &nbsp; &nbsp; &nbsp;Eq --&gt; E1 &nbsp; &nbsp;end &nbsp; &nbsp;subgraph walk ["DGA Walk (order depends on rdtsc)"] &nbsp; &nbsp; &nbsp; &nbsp;S1["seed_0"] --&gt;|"pow(s, step, p)"| S2["seed_1"] &nbsp; &nbsp; &nbsp; &nbsp;S2 --&gt;|"pow(s, step, p)"| S3["seed_2"] &nbsp; &nbsp; &nbsp; &nbsp;S3 --&gt;|"pow(s, step, p)"| S4["..."] &nbsp; &nbsp; &nbsp; &nbsp;S4 --&gt;|"pow(s, step, p)"| SN["seed_(q-2)"] &nbsp; &nbsp;end &nbsp; &nbsp;S1 -.-&gt;|"= g^e mod p\n(random start)"| cyclic_group &nbsp; &nbsp;S2 -.-&gt;|maps to| E3 &nbsp; &nbsp;S3 -.-&gt;|maps to| Eq</code></p>

<h2>From Group Elements to Domain Names</h2><p>Each group element is a 32-bit integer. Turning it into a domain name is the final step, handled by <code>transform11</code>. This is less mathematically elegant and more of a traditional mixing function, but it has a nice property: every character position in the domain uses a <em>different</em> currency rate.</p><p>The algorithm cycles through the full list of parsed currencies (31 in the example above). For a domain of length 18, that means character 0 is influenced by USD, character 1 by HRK, character 2 by MXN, character 3 by GBP, and so on. Each character is computed by:</p><ol><li data-list-item-id="e1b4d60fdb8fc1f153baf8a99855a0b35">Multiplying the currency's 3-letter name (packed as a 32-bit int) and its 64-bit floating-point rate by large constants</li><li data-list-item-id="ec05b47f97cd63ed0295b790fd5474c85">XORing and shifting the result with the current seed and the days-since value</li><li data-list-item-id="e2f1e2c5d769b5e8978ca12f1d05cf791">Taking the result modulo 26 (for positions 2+) or modulo 36 (for the last two positions, allowing digits)</li><li data-list-item-id="e589b38ae5aa632fba755388fc26bd71c">Adding the ASCII offset for 'a'</li></ol><p>The domain length itself is derived from the seed XORed with a rate-dependent value, bounded between 12 and 18 characters. All domains use the <code>.com</code> TLD.</p><p>A trace from the PoC output shows the mixing in action:</p><p><code>seed: 0xa13c9652 &nbsp; &nbsp;mixing in USD's rate &nbsp; &nbsp;mixing in HRK's rate &nbsp; &nbsp;mixing in MXN's rate &nbsp; &nbsp;mixing in GBP's rate &nbsp; &nbsp;... &nbsp; &nbsp;mixing in ZAR's rate &nbsp; &nbsp;domain: rrpohktjlscncqxvt3.com seed: 0x558af439 &nbsp; &nbsp;mixing in USD's rate &nbsp; &nbsp;... &nbsp; &nbsp;domain: wjavcjhazzxyxotkbi.com</code></p>

<p>Each domain is a fingerprint of the entire exchange rate vector, filtered through one specific element of the cyclic group.</p><h2>The Full Pipeline</h2><p>Putting it all together:</p><p><code>flowchart LR &nbsp; &nbsp;ECB["ECB XML\n31+ currency rates"] --&gt; DateSelect["Select last\nTuesday's rates"] &nbsp; &nbsp;Earth["earthtools.org\nUTC timestamp"] --&gt; DateSelect &nbsp; &nbsp;DateSelect --&gt; Mix["XOR/multiply\nrates + days_since"] &nbsp; &nbsp;Mix --&gt; TableLookup["Lookup table\n→ prime p, order q"] &nbsp; &nbsp;TableLookup --&gt; GenFind["Sieve primes,\nfind generator g"] &nbsp; &nbsp;GenFind --&gt; GroupSetup["seed = g^rand mod p\nstep = g2^rand mod q"] &nbsp; &nbsp;GroupSetup --&gt; Walk["Iterate:\nseed = seed^step mod p"] &nbsp; &nbsp;Walk --&gt; CharMix["Mix seed with\ncurrency rates"] &nbsp; &nbsp;CharMix --&gt; Domains["22-28 domains\nper config"]</code></p>

<p>Seven configs were observed in the wild, each with its own embedded table, XOR constants, and currency count (36 or 48). Each malware variant embedded two configs that ran per rotation -- the first generating 22 domains, the second 28, yielding 50 domains total. Across the observed campaign, domains were registered 2-5 days ahead of use through "Domain Context" registrar with Regway nameservers, all resolving to infrastructure at 5.196.181.244 and 46.105.251.1.</p><h2>Why this matters</h2><p>Compare Bedep's approach with its contemporaries:</p><table class="table"><thead><tr><th>Family</th><th>DGA Technique</th><th>Seed</th></tr></thead><tbody><tr><td>Conficker.C</td><td>Date + simple arithmetic</td><td>Current date</td></tr><tr><td>Gamaredon</td><td>Nested character-range loops</td><td>Hardcoded ranges</td></tr><tr><td>Necurs</td><td>CRC32 hash of date components</td><td>Date + constant</td></tr><tr><td>Matsnu</td><td>Dictionary word concatenation</td><td>Days since epoch</td></tr><tr><td><strong>Bedep</strong></td><td><strong>Cyclic group walk mod p</strong></td><td><strong>ECB exchange rates</strong></td></tr></tbody></table><p>Every other DGA on this list can be pre-computed arbitrarily far into the future. Bedep cannot -- because Tuesday's exchange rates don't exist until Tuesday. You can sinkhole Conficker's domains for next year during your coffee break. For Bedep, you have to wait for the ECB to publish, then race the botmaster to register the domains.</p><p>The mathematical guarantee is real: the cyclic group structure ensures exactly q - 1 distinct domains per rotation with no collisions and no wasted iterations. The primitive root construction ensures the generator produces every element. The precomputed tables avoid expensive factorization at runtime. The exchange rate seed provides unpredictable entropy from a trusted, globally-consistent, publicly-verifiable source.</p><p>This is not someone who copy-pasted a DGA from a forum. The author understood multiplicative groups modulo primes, knew how to find primitive roots, precomputed smooth-order primes offline, and wired the whole thing to the European Central Bank's daily publications. Whether they learned this from a university course, a textbook, or a cryptography library's source code, the result is unmistakable: this is applied algebra, deployed in production, at scale.</p><p>The original ASERT analysis is preserved on the <a href="https://web.archive.org/web/20160311083109/http://www.arbornetworks.com:80/blog/asert/bedeps-dga-trading-foreign-exchange-for-malware-domains/">Wayback Machine</a>. The proof-of-concept implementation was published on <a href="https://github.com/arbor/bedep_dga">ASERT's GitHub</a>. The sample analyzed here is <code>e5e72baff4fab6ea6a1fcac467dc4351</code> (MD5) /&nbsp;</p><p><code>d0fb1b66b6e4da395892327be9f39adb4533e7759ace39f67bdde0bb1cdaef35</code> (SHA256).</p><p>&nbsp;</p><p><em>Credits: The DGA was originally reversed by Dennis Schwarz at Arbor Networks / ASERT. This post builds on his work, focusing on the mathematical structure he identified but didn't fully unpack.</em></p>

A closer look at how Bedep used foreign exchange data and advanced math to generate hard-to-predict domains, making its command-and-control infrastructure more difficult for defenders to block and disrupt

When Malware Authors Study Algebra: The Group Theory Inside Bedep's DGA

A VM-obfuscated backdoor observed on a single machine in the UK, operated for one year, and vanished without a trace. 

Chasing an Angry Spark

SR. MALWARE ANALYST

Mgr, Threat Analysis Engineering

<p>Malicious software is often designed to hide its true behavior, wrapping its underlying logic in layers that make it difficult to analyze. “Unpacking” is the process researchers use to peel back those layers and reveal what the software is actually doing. But when standard tools run into unfamiliar or custom protections, this process can quickly become slow and highly manual. This project explores whether AI can help bridge that gap, assisting with the more repetitive parts of analysis so researchers can focus on validation, reasoning, and the parts of reverse engineering that still require human judgment.&nbsp;</p><p>Automated static binary unpacking is hard, and it tends to stop being hard in a useful way only when the packer is familiar. There are good unpackers out there, including some internal ones, but once you get out of their comfort zone, unsupported packers, custom routines, or slightly unusual logic can bring the whole process to a halt.&nbsp;</p><p>That makes unpacking a good example of where&nbsp;<a href="https://www.gendigital.com/blog/insights/research/engineering-the-future-of-agentic-threat-hunting">AI may genuinely help</a>. Across our broader work at Gen, we are increasingly using&nbsp;<a href="https://www.gendigital.com/blog/insights/research/engineering-the-future-of-agentic-threat-hunting">AI-assisted workflows</a> to accelerate parts of reverse engineering, technical correlation, and evidence organization, not as a substitute for expert analysis, but as a way to reduce friction in the slower, more repetitive parts of the job. The responsibility for verification and final conclusions still stays with the researcher.</p><p>From that perspective, the idea behind what we call the Last-Resort Unpacker is fairly simple: if AI is good at spotting patterns and translating logic across representations, could it help us recover payloads in cases where traditional static unpacking pipelines fail? We are not trying to solve the hardest forms of protection here. The goal is more pragmatic, to cover more real-world cases, reduce manual effort, and potentially extract logic that can later feed back into our regular unpacking workflows.</p><p>We came up with two approaches.</p><h2>High level design – Variant 1</h2><p>Given a sample to unpack, this simple premise has a few steps. Since we’ll go the most direct but also the riskiest way, let us call it <em>a carpe diem</em> variant.</p><p><strong>Identification:</strong>The first step is to identify which functions might be responsible for the unpacking and which buffers they are targeting. We have decided to use Gemini 2.5 Pro for our workload and complemented it with <em>radare2&nbsp;</em>reverse engineering framework to provide structured access to the disassembly. Once we identify the suspected decryption routine and the corresponding buffers, we may proceed to the translation.</p><p><strong>Translation:</strong> The next step relies on Gemini’s capabilities to rewrite the identified functions into their pythonic representation with prescribed function signatures.</p><p><strong>Verification:</strong> Now we have a Python code that hopefully faithfully represents the machine code identified in the first step. Now comes up the time to admit that we will be cheating on the initial assignment and we have to ensure that we will not be caught. We can easily statically check whether the source code is a valid source code. Now comes the tricky part – we have to verify that the product Python code does not have undesirable side-effects, be it from simple hallucinations or worse – due to hypothetical prompt injection. We have decided to do a strict abstract syntax tree (AST) verification which permits only certain keywords, operations, imports, and calls. If we obtain something that does not pass these criteria, then we have an interesting research case. In the other case, we may proceed to unpacking.</p><p><strong>Unpacking:</strong> Using the verified script, we attempt to do extraction on the source sample. Being paranoid, we shall use read-only environment with limited network access. If we succeed, we have not only an unpacked buffer but also an extraction script that we can use to improve our regular unpacking capabilities.</p><h2>High level design – Variant 2</h2><p>Now that we have attempted to do the most straightforward way, we can try to be a bit cleverer. Given the assumption that we can identify parts of the code responsible for the unpacking, adding two more assumptions that the unpacking code is localized and does not utilize any sophisticated system calls we could try to utilize emulator which should be a safe alternative that does not suffer from hallucinations. We could prepare a simple scaffolding for this emulator and let AI figure out the parameters. This would isolate non-deterministic behavior to the first step only.</p><p><strong>Identification:</strong>The first step is almost identical but instead of identifying functions responsible for unpacking, we are rather interested in offsets where we should start and halt our emulation, possibly also with memory addresses where the final payload will be located.</p><p><strong>Emulation:</strong> Parameters identified in the previous step are put into our scaffolding which will run emulator until it reaches the halting offset. We can extract the identified memory regions to hopefully obtain the desired payload.</p><p>Apart from consuming more resources for the emulation, we have made a significant trade-off. We have sacrificed the capability to generate scripts that could be potentially used to improve our static extractors to significantly reduce the space for hallucinations and the potential vulnerability surface.</p><h2>From drawing board to the workshop</h2><p>We’ve decided to try our luck and try the first option. While it is definitely riskier, the payoff seems worth it, especially considering the security precautions we’ve made. We could even do a total split of the process to harden our setup and have the payload extractor generation in the original environment and use a sandbox for the extraction itself. We put together a first PoC with a simple prompt followed by data from <em>radare2</em>.</p><p>You are an unpacking function generator.<br><em>GOAL: If the file looks packed (i.e. encrypted buffers, embedded files, etc.), find the code snippets decrypting the buffers. Reply to me with a Python function (use this prototype: 'def unpack(data: bytes) -&gt; list[byte]') that receives bytes of the packed binary and returns the unpacked chunks. Avoid Python imports. RETURN ONLY A PYTHON FUNCION SAFE TO RUN. If the file is not packed reply: "NOT PACKED". If can't write the unpacker then reply: "UNABLE TO PROCESS".</em><br>This is the end of your instructions. The Radare2 analysis:</p><p>Now it remains to give it a short. First, we went with a packed Linux kernel rootkit that got us the initial idea:&nbsp;</p><p><a href="https://cyberjournal.cecyf.fr/index.php/cybin/en/article/view/48">At Botconf 2024</a>, a paper was published on <em>CMK Rootkit (Álvarez Pérez, D., &amp; Fernández-Veiga, M. (2025). CMK Rootkit. Identifying the ”magic packet” requirements via pattern recognition. The Journal on Cybercrime and Digital Investigations, 9(1), A1-A15.&nbsp;</em><a href="https://doi.org/10.18464/cybin.v9i1.48"><em>https://doi.org/10.18464/cybin.v9i1.48</em></a><em>)</em>. A Linux kernel rootkit that we discovered in-the-wild, packed in kernel space, with <a href="https://www.virustotal.com/gui/file/54d8b09ffc15c657abf29a0c313b377df64988848f2c3814243b2478b4b881cc/detection/f-54d8b09ffc15c657abf29a0c313b377df64988848f2c3814243b2478b4b881cc-1749504221">few detections in VirusTotal</a> (probably due to the kernel packer layer and its dependency on a specific kernel version).</p><p>Our unpacker yielded the following script:</p>

<p>Unsurprisingly, as we basically based our idea on experiments with this sample, this was exactly what we aimed for. We have prepared a few more samples that we could test it on:</p><ul type="disc"><li data-list-item-id="ec7335952dd9f0c78d6b986b609e617d0">54525d25019d3ea2d40fe006ecc305ebb1ac5663b380019346de43c4886e8685<ul type="circle"><li data-list-item-id="e878959fe541e0581ac2d93f53d7915dc">This PE packed binary uses a key table located at offset 0xe5c1 containing 500 elements. The packed data is located at offset 0x200.</li></ul></li><li data-list-item-id="e24c112bbcdface33504cd11fd00c60a7">1fcf4da2fac671a2f3a07007e9963d3e1063dcfb0b1a0934c66082e8233d7686<ul type="circle"><li data-list-item-id="e999fd8e60c992d59154f20daef223bd0">This PE file contains a payload encoded as a word-based substitution cipher. It implements anti-sandbox protection that checks the available memory (via GlobalMemoryStatusEx) and the system ticks (via GetTickCount64) to determine if the underlying system is a sandbox.</li></ul></li></ul><h2>Closing thoughts</h2><p>This experiment fits into a broader shift in how we are using AI in technical research. The value is not in handing over reverse engineering to a model and hoping for the best. It is in identifying narrow, high-friction parts of the workflow where pattern recognition and code translation can save analysts time, while validation, judgment, and final conclusions remain firmly in human hands.</p><p>A last-resort unpacker will not solve the hardest cases, and it is not a replacement for established tooling or expert analysis. Advanced multi-layer protections, virtualization, and heavily environment-dependent logic still remain difficult territory. But even within those limits, the approach already shows practical value. If it helps recover payloads from unsupported packers, reduces manual effort in repetitive cases, or produces reusable logic that can later improve our existing unpacking pipelines, then it is worth pursuing.</p><p>Seen from that perspective, the point is not that AI is replacing reverse engineers. It is that it can make experienced researchers faster when conventional automation runs out of road.</p>

Exploring how AI can assist in unpacking protected binaries, recovering payloads from unsupported packers, while reducing repetitive analysis

Building a last-resort unpacker with AI

<h2>Key points</h2><ul type="disc"><li data-list-item-id="e4b810198ac9891110da1771c3f2d0397">Gen Threat Labs has identified Remus, a new 64-bit infostealer we attribute to the infamous Lumma Stealer family – emerging in the wake of Lumma’s takedown and the doxxing of its alleged core members.</li><li data-list-item-id="ede8006689bbfaba0d6fa856478b3ea79">In this technical blog post, we detail the compelling evidence tying Remus to Lumma across multiple dimensions.</li><li data-list-item-id="ef3f0d531ccf019ab00b98a38b3c43c17">We also describe a previously undocumented Application-Bound Encryption bypass employed specifically by Remus and Lumma.</li><li data-list-item-id="ee0040d0e9463ac082d24fcdbfd7af133">The first Remus campaigns date back to February 2026, with the malware switching from Steam/Telegram dead drop resolvers to EtherHiding and employing new anti-analysis checks.&nbsp;</li></ul><h2>Introduction</h2><p>When the security industry talks about information stealers, Lumma Stealer, without a doubt, has become the notorious icon of this landscape. Not only could it count itself among the most sophisticated, technically advanced, and widespread stealers-as-a-service in the world, but it was also described in a variety of blog posts from basically everyone in the industry, including us.</p><p>In this analysis, we describe a new variant of Lumma Stealer that we call Remus, a new x64 build which we suspected might occur in the foreseeable future after the doxxing of Lumma authors from late August to October 2025. And the future is here.</p><p>Remus brings the same stealing arsenal to the table as we already know from Lumma, capable of stealing stored browser passwords, cookies, cryptocurrency, and much more. However, rather than revisiting Lumma's well-documented capabilities, we focus on the remarkable resemblance between Remus and Lumma, as well as the new techniques Remus introduces, including the use of EtherHiding to resolve C2s, replacing the traditional use of Steam and Telegram dead drop resolvers, and additional anti-analysis checks.&nbsp;</p><p>The attribution of Remus to Lumma is many-fold and described thoroughly throughout the blog post. The main indicators, to name a few, are the use of the same string obfuscation technique, AntiVM checks, direct syscall/sysenter handling, indirect control flow obfuscation, and, most importantly, an almost identical approach to bypassing AppBound Encryption, which we’ve only seen used explicitly by Lumma to date.</p><p>With that said, we can still see active Lumma campaigns all around the world, which makes Remus not a replacement, but a continuous evolution.</p><h2>Development timeline</h2><p>Before diving into the technical details, it is worth noting that during our hunting efforts, we came across several test samples, which even carry a <code>testbuild</code> label embedded directly in the binaries (see Figure 1). We are internally referencing these builds as Tenzor (based on encrypted strings). These test builds are already 64-bit and structurally very close to Remus, suggesting they represent a transitional step, or perhaps even a testing ground, between Lumma and Remus.</p>

<p>This also brings us to the name itself. Both Tenzor and Remus have left a string artifact in the same part of the code, referencing the <code># TENZOR LOG</code> and <code># REMUS LOG</code> strings. Since we have been tracking only test builds with the Tenzor string and Remus is the variant that is being actively distributed in live campaigns, we took the liberty of naming the new x64 Lumma variant after the latter string – Remus.</p>

<p>Notably, all the Tenzor samples carry a build date of September 16, 2025, in their stack-encrypted strings, which is months before the first Remus samples began appearing in the wild at the turn of January and February 2026. The build timing closely coincides with a period when Lumma Stealer suffered a major blow through a doxxing campaign that exposed alleged core members and severely disrupted its operations. This may suggest that some of Lumma’s authors split off, or that Lumma decided to rebrand under a new name in the midst of the doxxing fallout. Nevertheless, at Gen Threat Labs, we track both Remus and Tenzor as variants of Lumma Stealer. That said, the only samples bearing the Tenzor name are the ones that also carry the <code>testbuild</code> label. All others are identified as Remus.</p>

<h2>Similarities between Remus and Lumma</h2><p>When we first started analyzing Remus, something felt familiar, and for good reason. Many of the techniques and design patterns we encountered in Remus closely mirrored those we had already seen in Lumma Stealer. The main difference is that Lumma was 32-bit while Remus is 64-bit, which naturally introduced some variations. Yet, when we looked past the 32-bit versus 64-bit differences and stripped away the obfuscation layers, what remained was strikingly familiar.</p><p>In the following subsections, we highlight the most compelling evidence of a direct connection between Remus and Lumma. Note that this is not an exhaustive list. The overlaps are far more numerous, but we selected just a few that we believe speak for themselves.</p><h3>Forgotten dead drop resolver and string obfuscation&nbsp;</h3><p>For a malware researcher, strings are among the most valuable resources during reverse engineering, and in the case of attributing Remus to Lumma, they proved no different.&nbsp;</p><p>Both Remus and Lumma use a virtually identical mechanism for string obfuscation. The encrypted string is first assembled on the stack using a series of various forms of the <code>mov</code> instruction, followed by a decryption loop that transforms the data byte by byte. The transformation is often further obscured by MBA (Mixed Boolean-Arithmetic) obfuscation and is either inlined or placed in a standalone function. In any case, each string is protected using a unique transformation, making it very difficult to build a universal static decryptor. As a result, emulating the decryption loops is likely the most effective approach for dealing with encrypted strings in both Remus and Lumma.&nbsp;</p>

<p>Notably, the decryption loops are often preceded by several <code>nop</code> instructions (Lumma) or a single <code>nop</code> instruction encoded using multiple bytes (Remus), likely inserted as padding during a custom compilation pass. We are aware that the compilers themselves can emit <code>nop</code> paddings. Still, in both Remus and Lumma, these sequences go beyond the typical, making it yet another indicator linking the two together.</p><p>After decrypting all strings in both Remus and Lumma and comparing them side by side, we found roughly 100 completely identical strings. Most of these, however, could be attributed to virtually any information stealer. The more telling discovery came when we looked at the strings that were not identical – most of them turned out to be semantically the same, just slightly refactored. This alone would already be a strong indicator.&nbsp;</p><p>However, what ultimately confirmed our theory was shifting the string comparison from Lumma vs. Remus to Lumma vs. Tenzor, as Tenzor effectively acts as a bridge between the other two – many of the strings we had previously matched only semantically between Remus and Lumma were still present in Tenzor in their original, unmodified form, directly matching Lumma’s. At the same time, Tenzor also contained very specific strings found exclusively in Remus but not in Lumma, such as <code>B9%????4rnO/@NQe?Nx*</code>, used as a wildcard mask in the ABE-bypass (which we will discuss later), firmly linking it to both sides.</p>

<p>On top of that, among the decrypted Tenzor strings, we also found a Steam dead drop resolver <code>hxxps[://]steamcommunity[.]com/profiles/76561199861614181</code>, which turned out to be the exact same resolver present in multiple confirmed Lumma samples, namely:</p><ul><li data-list-item-id="e7c7ac2aae55af0df2c596fe8463f5a97">002f714f93bed53f165129a820c2d5b72227f1cafac43be19e5e223ce219a5e1 (Lumma)</li><li data-list-item-id="ea0c5ca160e92372f6b8b681415725a00">066c4ab954fc1270ee62c0d7c582c4c691e58e0ffef0c654bc204a46e440d16d (Lumma)</li><li data-list-item-id="e2eae0f6619eb5e4ffb9d1e84b3e057d6">0683f353cf3e101f721f1658e2a554ff7888ff9f2c32e23ceb3d23876864a264 (Lumma)</li><li data-list-item-id="efe40dcac54b87ce148882d49b97105a6">0580ebf601989457f0708799b431fd4d9f5e59d98838282d72936099aa6636da (Tenzor)</li></ul>

<h3>Application-bound encryption bypass</h3><p>Another very strong indicator tying Remus and Lumma together is the way they bypass Application-Bound Encryption (ABE), as both employ a highly specific technique that, until now, we have only observed and have been actively tracking in Lumma Stealer.</p><p>The technique involves injecting a very short shellcode (less than 100 bytes) into the browser process to decrypt the <code>v20_master_key</code>. However, unlike most techniques relying on injection, Lumma as well as Remus do not use this shellcode to call <code>IElevator::Decrypt</code> with the key obtained from the <code>Local State</code> file (the <code>[“os_crypt”][“app_bound_encrypted_key”]</code> JSON field). Instead, it locates the <code>v20_master_key</code> directly in the browser’s process memory, where it is stored in an encrypted form protected by <code>CryptProtectMemory</code> with the <code>CRYPTPROTECTMEMORY_SAME_PROCESS</code> flag. It then calls the complementary <code>CryptUnprotectMemory</code> with the same flag from within the browser’s context to decrypt it.</p><p>It is important to note that this in-memory encrypted form of the <code>v20_master_key</code> is protected with a <strong>different key</strong> than the one used to protect the key on disk – it is a separate protection layer that Chromium browsers use to safeguard the key while it resides in memory at runtime. However, since the key is protected with the <code>CRYPTPROTECTMEMORY_SAME_PROCESS</code> flag, decryption can only be performed by the same process that encrypted it, which is precisely why injection into the browser process is necessary in this specific bypass. For the curious, we discussed this topic in more detail in our recent&nbsp;<a href="https://www.gendigital.com/blog/insights/research/voidstealer-abe-bypass" target="_blank">VoidStealer blog post</a>.</p><p>From this point on, we will walk through the ABE bypass as implemented in Remus, noting any differences from Lumma’s implementation where applicable. Where no differences are explicitly mentioned, the two implementations work either identically or very similarly.&nbsp;</p><p>So how does Remus find the protected <code>v20_master_key</code>? It begins by walking the browser’s PEB module list, looking for two modules in a single pass: <code>dpapi.dll</code> and the browser DLL (e.g., <code>chrome.dll</code>).&nbsp;</p><p>When <code>dpapi.dll</code> is found, Remus manually parses its PE export directory, reading the DOS header, PE header, and export table through repeated <code>NtReadVirtualMemory</code> syscalls. For each exported function name, it computes a seeded CRC32 hash and compares it against the pre-computed hash&nbsp;corresponding to&nbsp;<code>CryptUnprotectMemory</code>. Essentially, a typical API-hashing, but in a remote process. Once a match is found, it&nbsp;resolves the function’s RVA to obtain its absolute address in the browser’s address space.</p><p>When the browser DLL is found during the same pass, Remus decrypts a hex pattern <code>488d058bcc8d02488901488b024889415b488d41</code>, which was encrypted by the same string obfuscation technique described earlier and stores the value <code>0xEFF87</code> (which corresponds to <code>11101111111110000111</code> in binary) into a variable we labeled as <code>wildcard_mask</code> (see&nbsp;Figure&nbsp;8).&nbsp;</p>

<p>The hex pattern corresponds to a sequence of opcodes that Remus searches for within the browser DLL (e.g., <code>chrome.dll</code>), while the wildcard mask, read from the least significant bit, indicates which bytes must match exactly and which should be treated as wildcards. Lumma does the same but takes a different approach to wildcarding. Instead of a hex mask, it uses a 20-character string <code>B9%????4rnO/@NQe?Nx*</code>, where ? denotes a wildcard and any other character means the byte must match exactly. Notably, this exact string also appears in Tenzor builds, which directly ties Tenzor to the Lumma codebase.</p>

<p>Looking into <code>chrome.dll</code>, we can see that the pattern is designed to locate a <code>LEA</code> (Load Effective Address) instruction that loads a 32-bit displacement pointing to the <code>os_crypt_async::Encryptor</code> virtual function table (vftable). The reason for specifically targeting the <code>os_crypt_async::Encryptor</code> class is that it holds the protected <code>v20_master_key</code>.</p>

<p>Once the pattern is found, Remus reads the 32-bit displacement at <code>pattern_address + 3</code> and computes the absolute address of the <code>os_crypt_async::Encryptor</code> vftable using the formula: <code>target_addr = pattern_addr + disp32 + 7</code> (since the <code>LEA</code> instruction is 7 bytes long and the displacement is relative to the next instruction).&nbsp;It then scans the browser’s memory for this 8-byte vftable pointer by enumerating committed, readable memory regions via <code>NtQueryVirtualMemory</code> and reading each one into a local buffer via <code>NtReadVirtualMemory</code>. Wherever a match is found, it marks the start of an <code>os_crypt_async::Encryptor</code> instance in memory, as the vftable pointer sits at the very beginning of the object. From there, extracting the protected <code>v20_master_key</code> is just a matter of walking the structure at known offsets.&nbsp;</p>

<p>After resolving all the necessary&nbsp;addresses, Remus allocates&nbsp;a buffer&nbsp;in the browser process via <code>NtAllocateVirtualMemory</code>, which serves as both the copy destination and the in-place decryption target.&nbsp;It then constructs&nbsp;a 51-byte&nbsp;shellcode (shown in Figure 12), allocates a second buffer with the <code>PAGE_EXECUTE_READWRITE</code> protection constant for the shellcode itself, and&nbsp;writes it into the browser process via <code>NtWriteVirtualMemory</code>. The shellcode is then executed via <code>NtCreateThreadEx</code>, and Remus waits for its completion using <code>NtWaitForSingleObject</code>.&nbsp;Once the <code>v20_master_key</code> is decrypted, Remus simply reads it from the buffer it previously allocated (and, therefore, already knows its&nbsp;address) via <code>NtReadVirtualMemory</code>.</p>

<p>The injected shellcode differs slightly between Remus and Lumma, but both fundamentally do the same thing – copy the protected <code>v20_master_key</code> into a pre-allocated buffer and jump to <code>CryptUnprotectMemory</code> to decrypt it in place. Both construct the shellcode on the stack, patching in the resolved addresses before writing it into the browser process. The only real difference is that Remus produces a more compact variant (51 vs 62 bytes) by reusing registers. Concrete examples of the injected shellcodes are shown in Figure 13 (Remus) and Figure 14 (Lumma).</p>

<p>Another detail linking the two is that when no browser process is already running, or when injection into an existing one fails, both Remus and Lumma spawn a new one on a separate, hidden desktop, preventing any visible windows from appearing on the user’s screen. They first attempt to open an existing desktop using <code>OpenDesktopW</code> and fall back to creating a new one via <code>CreateDesktopW</code> if it does not yet exist. A new browser instance is then launched via <code>CreateProcessW</code> with <code>STARTUPINFOW.lpDesktop</code> set to this desktop. The only difference is that Lumma uses a hardcoded desktop name&nbsp;<code>ChromiumDev</code> (or previously also <code>ChromeBuildTools</code>), while Remus generates a random 16-character alphanumeric string using a Mersenne Twister PRNG, a natural evolution rather than a change in approach.</p><p>Furthermore, both Remus and Lumma also employ SYSTEM token impersonation as an alternative method to bypass ABE. Interestingly, the two families differ in which method they prefer: Remus attempts SYSTEM elevation first and falls back to shellcode injection, while Lumma tries injection first and resorts to SYSTEM elevation only if it fails. That said, SYSTEM token impersonation for ABE bypass is a well-known technique widely used across many stealer families. What, however, is highly distinctive is the injection-based bypass described above, which to our knowledge has only been used by Lumma and now also Remus.&nbsp;</p><h3>AntiVM CPUID checks</h3><p>Another identical technique shared by Remus and Lumma is their anti-VM check based on the&nbsp;<code>cpuid</code>&nbsp;instruction with&nbsp;<code>EAX</code>&nbsp;set to&nbsp;<code>0x40000000</code> – the hypervisor vendor identification leaf. When executed inside a virtual machine, the processor returns the hypervisor’s vendor signature in <code>EBX:ECX:EDX</code>. Both Remus and Lumma specifically check the&nbsp;<code>ECX</code>&nbsp;portion (4 bytes) against five known hypervisor signatures: KVM (<code>KVMKVMKVM</code>), QEMU/TCG (<code>TCGTCGTCGTCG</code>), VMware (<code>VMwareVMware</code>), VirtualBox (<code>VBoxVBoxVBox</code>), and Xen (<code>XenVMMXenVMM</code>). Notably, both check <strong>the same substrings</strong> of hypervisor names <strong>in the same order</strong>, and the checked substrings are obfuscated.&nbsp;</p><p>The decompiled code performing the check can be seen in Figure 15 (Remus) and Figure 16 (Lumma). For clarity, we omitted the decryption loops from the Lumma listing, but they are the same decryption loops we described earlier.</p>

<h3>Crypter check</h3><p>When executed without a protective layer, both Remus and Lumma display a warning dialog before proceeding with their malicious payloads (see Figures 17 and 18). The purpose of this mechanism is twofold: to discourage distributors from spreading the raw, unprotected executables, which are more easily detected by security products, and to prevent less skilled affiliates from accidentally infecting their own machines.</p>

<p>This type of check is relatively rare. So far, only a handful of families have been observed employing it – namely, <a href="https://outpost24.com/blog/lummac2-anti-sandbox-technique-trigonometry-human-detection/">Lumma</a>, <a href="https://research.checkpoint.com/2025/rhadamanthys-0-9-x-walk-through-the-updates/" target="_blank">Rhadamanthys</a>, Remus, and <a href="https://www.gendigital.com/blog/insights/research/defeating-aurastealer-obfuscation">more recently also AuraStealer</a>, albeit AuraStealer takes a slightly different approach (rather than simply displaying a warning and waiting for the user to click <code>Yes</code> or <code>OK</code>, it additionally requires the user to enter a randomly generated code shown in the dialog).&nbsp;</p><p>However, despite the surface-level similarity, the underlying implementations differ. <a href="https://research.checkpoint.com/2025/rhadamanthys-0-9-x-walk-through-the-updates/">Rhadamanthys displays its warning dialog</a> using <code>MessageBoxW</code>, whereas both Remus and Lumma invoke it through a direct <code>NtRaiseHardError</code> syscall.&nbsp;</p><h3>Direct syscalls/sysenters</h3><p>Both Remus and Lumma make use of direct syscalls/sysenters. While their implementations differ in some details, mostly as a natural consequence of the 32-bit vs 64-bit architecture, the overall design is strikingly similar.</p><p>One of the first things both do upon execution is that they enumerate all <code>Nt</code>-prefixed exports from <code>ntdll.dll</code> and build a lookup table mapping their name hashes to the corresponding Syscall Service Numbers (SSNs). The process is the same in both cases: they walk the <code>ntdll.dll</code> export directory, hash each matching export name, and scan the first 32&nbsp;bytes of each function’s prologue to extract the SSN from the <code>mov eax, &lt;SSN&gt;</code> instruction. The extracted SSN is then stored alongside the export’s name hash in a hash-to-SSN lookup table.&nbsp;</p>

<p>To invoke a specific syscall/sysenter, both perform a linear scan of the lookup table until they find an entry whose hash matches the requested function. The SSN from the matching entry is then passed to a central dispatcher, which we refer to as <code>lumma_sysenter</code> and <code>remus_syscall</code>. The calling conventions of those dispatcher functions are nearly identical: the first argument is the SSN, followed by the argument count and the variadic arguments themselves. The only difference is that Lumma expresses the argument count in bytes (<code>number_of_arguments × 4</code>), whereas Remus passes the actual count directly.</p>

<p>The dispatchers themselves look different at first glance, but this is mostly a consequence of ABI differences between 32-bit and 64-bit code. The core logic is the same: arrange the syscall/sysenter arguments and invoke the kernel. Remus does so directly via the&nbsp;<code>syscall</code>&nbsp;instruction. Lumma, on the other hand, resolves a dispatcher address during the hash-to-SSN initialization through a fallback chain: it first attempts to resolve the <code>Wow64Transition</code> export from <code>ntdll.dll</code> using API-hashing, then tries the <code>TEB-&gt;WOW32Reserved</code>, and finally, if that value is <code>NULL</code>, falls back to a hardcoded <code>sysenter</code>stub. Each of these fallback mechanisms ultimately achieves the same outcome – a transition from user-mode 32-bit code into the kernel.</p>

<p>Separately from the 32-bit <code>sysenter</code> dispatch, Lumma also employs Heaven’s Gate, a&nbsp;technique that allows 64-bit code to be executed from within a 32-bit process on a 64-bit operating system. Lumma uses it specifically when interacting with 64-bit browsers (during the ABE bypass) to call native 64-bit <code>ntdll.dll</code> functions that have no NtWow64 equivalents – namely <code>NtCreateThreadEx</code> to start the injected thread, <code>NtFreeVirtualMemory</code> for clean up, and <code>NtQueryVirtualMemory</code> to query the browser’s memory layout. The remaining cross-process operations, such as memory reads, memory allocations, and shellcode writes, are handled through standard NtWow64 sysenter calls (<code>NtWow64ReadVirtualMemory64</code>, <code>NtWow64AllocateVirtualMemory64</code>, and <code>NtWow64WriteVirtualMemory64</code>). Since Heaven’s Gate is inherently a WoW64 technique applicable only to 32-bit processes running on 64-bit systems, and Remus is a 64-bit binary, it has no equivalent. Remus simply uses direct syscalls for all these operations.</p><h3>Shared code patterns</h3><p>Another striking similarity is the layout of many functions, which shows a remarkable resemblance and, in some cases, is nearly identical (if we disregard the obfuscation and differences caused by 32-bit vs 64-bit code). While there are many such functions, we highlight two concrete examples. The first is the heap allocation wrapper, which Remus and Lumma implement in a virtually identical manner, as illustrated in Figures&nbsp;24 and 25. Furthermore, the same holds for other memory helpers, such as the reallocation and deallocation wrappers.&nbsp;</p>

<p>The second example is the clipboard-stealing routine (Figures 26 and 27). Both implementations follow the same sequence: they open the clipboard, retrieve its contents, convert it from UTF-16 to UTF-8, decrypt the output filename <code>Clipboard.txt</code> using a stack-based decryption loop, and finally append the result to the exfiltration archive. The only difference is that Remus wraps each API call in a thin stub, which, however, might just be a result of different compiler optimization.</p>

<p>Notably, although the vast majority of API calls are obfuscated through API hashing, the clipboard functions <code>OpenClipboard</code>, <code>GetClipboardData</code>, and <code>CloseClipboard</code> are among the very few unobfuscated imports in both binaries.</p><p>Equally notable is the entry point structure. Both Remus and Lumma begin executing their malicious logic directly from the PE entry point (the&nbsp;<code>start</code>&nbsp;function), with no runtime initialization whatsoever. In a typical C/C++ binary, the entry point calls the CRT startup routine, which sets up the heap, initializes global variables, registers exception handlers, processes the command line, and invokes static constructors before eventually calling&nbsp;<code>main</code>. However, neither Remus nor Lumma follows this pattern. Instead, both jump directly from the entry point into their core logic: resolving modules and APIs, performing anti-analysis checks, initializing C2 communication, and exfiltrating data, ending with a direct call to <code>ExitProcess(0)</code>. This suggests both were compiled without linking to the standard C runtime, likely a deliberate choice to minimize the binary size and reduce unnecessary dependencies.</p><p>The structural similarities extend further. Both binaries share the same section layout, with each section serving an identical semantic role. Even the C2 configuration follows the same pattern: in both cases, the encrypted blob, key, and nonce are statically embedded in the <code>.rdata</code> section and decrypted at runtime using ChaCha20.</p><p>To summarize, we strongly believe the degree of similarity between the two codebases is too deliberate to be a coincidence, pointing to a single, shared origin.</p><h3>Indirect control flow obfuscation</h3><p>Finally, both Remus and Lumma make use of control flow obfuscation by replacing direct jumps with indirect ones, where the target is read from an offset stored in the <code>.data</code> section. As shown in Figure 28, this technique takes several forms. In its simplest case, the target address is resolved by a single pointer dereference (highlighted in yellow). In more complex cases, it extends to a full jump table, where a computed index selects among several target addresses stored consecutively in the <code>.data</code> section (highlighted in orange). Lastly, in some cases, the target address is first loaded into a register (highlighted in blue) and then jumped to via a register-based indirect jump (highlighted in pink).</p>

<p>Although functionally equivalent to normal jumps, the indirection&nbsp;complicates the control flow analysis in two ways. First,&nbsp;some of the indirect jump targets cannot be statically determined (for example, when the register holding the target address can be set in multiple different preceding basic blocks, each potentially loading a different target), leaving the control flow graph incomplete as the connections between basic blocks are lost. Second, some of these orphaned blocks end up being misidentified as standalone functions, further disrupting function boundary detection and leading to a broken, incomplete decompiler output. Notably, Figure 28 also provides another glimpse of the <code>nop</code> paddings discussed earlier.</p>

<p>Both binaries contain hundreds of these indirect dispatch points, and once again, if we set aside the minor differences arising from the 32-bit vs. 64-bit differences, the obfuscation is virtually identical. Although removing the obfuscation entirely requires more effort, the IDA’s decompiler output can be significantly improved by marking the referenced offsets as constants. For those interested, we covered this trick in our <a href="https://www.gendigital.com/blog/insights/research/defeating-aurastealer-obfuscation">AuraStealer blog post</a>, along with other approaches for tackling control flow obfuscation.</p><h2>What’s new in Remus</h2><p>Having covered the key similarities between Remus and Lumma, let’s now focus on what is new in Remus. The core architecture is clearly inherited from Lumma. Still, several changes go beyond a straightforward 32-bit-to-64-bit port. These range from refactored strings and more thorough device fingerprinting to a different exfiltration archive format, a switch from FNV-1a to CRC32 for API hashing, and an overhauled C2 communication that has been restructured to deliver dynamic configurations incrementally rather than in a single large blob. &nbsp;</p><p>The most significant changes, however, are the replacement of traditional Steam/Telegram dead drop resolvers with blockchain-based C2 resolution using EtherHiding, a persistence technique allowing attackers to store malware-related data (such as domains, payloads, encryption keys, among others) on blockchain as a smart contract, and the introduction of additional anti-analysis checks.</p><h3>Dead drop resolvers via EtherHiding</h3><p>Both Remus and Lumma employ dead drop resolvers, a mechanism in which the malware does not contact its C2 server directly but instead retrieves the C2 address at runtime from an intermediary hosted on a legitimate platform. This makes the infrastructure significantly more resilient, as if a C2 domain is taken down, the dead drop can be adjusted to point to a new server without the need to distribute an updated binary. Moreover, the dead drop URLs typically reside on well-known, high-reputation services, making them more difficult for security vendors to block without collateral damage.</p><p>Where the two differ is in the choice of platform. Lumma relies on Steam profiles and Telegram channels, typically encoding C2 URLs using ROT-15, while Remus goes a step further, replacing these with Ethereum smart contracts. At runtime, it sends an <code>eth_call</code> JSON-RPC request to a hardcoded contract address via a public RPC endpoint and extracts the C2 URL from the hex-encoded response. Because blockchain data is decentralized and immutable, there is no platform operator to report abuse to, making the dead-drop effectively immune to takedowns.</p><p>Just like Lumma’s Steam profile URL, Remus stores the smart contract address separately from the static C2 configuration, as a stack-encrypted string. Notably, after the JSON response is retrieved, the C2 address is, at least for now, merely hex-encoded in the <code>result</code> field (no other obfuscation, such as ROT-15 in case of Lumma, is applied).</p>

<h3>Additional anti-analysis checks</h3><p>Remus introduces two additional anti-analysis mechanisms, both evaluated early during startup (before connecting to its C2). If either check fails, the malware silently terminates via <code>ExitProcess(0)</code>.&nbsp;</p><p>The first check targets sandbox and analysis tool DLLs. Remus walks the PEB's <code>InLoadOrderModuleList</code>, hashes the name of every loaded module using a CRC32 variant with a custom initialization constant, and compares the result against 11 pre-computed hashes stored in its <code>.rdata</code> section, each corresponding to a module commonly injected by analysis environments, including Avast sandbox (<code>snxhk.dll</code>), Sandboxie (<code>sbiedll.dll</code>), Comodo sandbox (<code>cmdvrt32.dll</code>, <code>cmdvrt64.dll</code>), and several others.&nbsp;</p>

<p>If no sandbox DLLs are detected, Remus proceeds by expanding the path&nbsp;<code>%UserProfile%\Documents\Outlook Files</code>, enumerating all&nbsp;<code>*.pst</code>&nbsp;files in that directory, and checking for the presence of&nbsp;<code>honey@pot.com.pst</code>, which would be treated as a sandbox environment.&nbsp;</p><h2>Summary</h2><p>In this analysis, we described our findings regarding a new x64 variant of Lumma Stealer, which we call Remus. We focused on various similarities and differences between Lumma and Remus, thoroughly describing the technical aspects of both. We also provided a timeline, referencing the very first test builds of Remus (historically called Tenzor), which correlate with the extensive doxxing of Lumma authors from late August to October 2025.</p><p>The key aspects that allowed us to attribute Remus as a new x64 version of Lumma are the use of the same string obfuscation technique, AntiVM checks, direct syscall/sysenter handling, indirect control flow obfuscation, and, most importantly, an almost identical approach to bypassing AppBound Encryption, which we’ve only seen used by Lumma to date.</p><p>Remus, however, is not merely an x64 port of Lumma. It also introduces a couple of novel techniques in how it operates, including the use of EtherHiding instead of a traditional approach of using Steam/Telegram as dead drop resolvers, as well as additional anti-analysis checks to evade a wider range of security vendors.</p><h2>Indicators of Compromise (IoCs)</h2><p>A complete IoC list is available on our <a href="https://github.com/gendigitalinc/ioc/tree/master/Remus">GitHub</a>.</p><h3>C2 domains</h3><p>hxxp[://]217[.]156[.]122[.]12:80<br>hxxp[://]217[.]156[.]122[.]57:80<br>hxxp[://]217[.]156[.]122[.]75:1378<br>hxxp[://]45[.]151[.]106[.]110:80<br>hxxp[://]80[.]97[.]160[.]155:80<br>hxxp[://]86[.]107[.]168[.]103:80<br>hxxp[://]94[.]231[.]205[.]229:28313<br>hxxp[://]adveryx[.]biz:6573<br>hxxp[://]backbou[.]biz:5902<br>hxxp[://]baxe[.]pics<br>hxxp[://]baxe[.]pics:48261<br>hxxp[://]borscer[.]biz:9592<br>hxxp[://]buccstanor[.]pics<br>hxxp[://]buccstanor[.]pics:28313<br>hxxp[://]buccstanor[.]pics:48261<br>hxxp[://]chalx[.]live:5902<br>hxxp[://]chromap[.]biz:4219<br>hxxp[://]coox[.]live:28313<br>hxxp[://]drymoge[.]biz:4192<br>hxxp[://]forestoaker[.]com:6290<br>hxxp[://]gluckcreek[.]online:48261<br>hxxp[://]intem[.]lat:9592<br>hxxp[://]interxo[.]biz:7481<br>hxxp[://]josegza[.]biz:8521<br>hxxp[://]krondez[.]com:28982<br>hxxp[://]lazzo[.]bet:3989<br>hxxp[://]managew[.]biz:5902<br>hxxp[://]navelum[.]biz:3201<br>hxxp[://]nitroca[.]biz:6782<br>hxxp[://]outcrol[.]biz:4895<br>hxxp[://]padaz[.]pics:4219<br>hxxp[://]parky[.]pics:3989<br>hxxp[://]prickaz[.]biz:2039<br>hxxp[://]remnane[.]biz:5692<br>hxxp[://]ropea[.]top:28313<br>hxxp[://]siltsoh[.]biz:7481<br>hxxp[://]texakgi[.]cloud:3849<br>hxxp[://]vinte[.]online<br>hxxp[://]vinte[.]online:28313<br>hxxp[://]woodena[.]biz:7821<br>hxxp[://]zadno[.]run:4219<br>hxxps[://]cheekiez[.]biz<br>hxxps[://]nobleckly[.]biz</p><p>&nbsp;</p><h3>Remus SHA-256 (Non-exhaustive)</h3><p>0a8f734f10400f7ae8fef591147e78dab6350089683be84c1cb6c82113cb1319<br>25e74a76f2f3601abcb20fd743a7e3cf3befd5a3838c7501af5d87d293233809<br>4428c3ffe2532f162f31d7573bbc1cca2299195421da3d8e8a3e535e9fc42b08<br>484e3ab5d425a97819f01dcc330e005dc444c51625bfdcd7ea9a3954018d1fc9<br>64db10e76b46be8db36e02993d36559bc3f86606c9ea955731872b716c8f0c69<br>788b56e9be2f1dd6a977dce0265f293ab42d3e8ffb287ab584e169fbf115da1f<br>8653d7158486aa10fc0078c3ca9318cd7ace05d4b3e6f3b1fb84ffb7a6a339ec<br>a4f111e5425690fcd384c62ecb5b57b0f645925572af3541748e01d810cd2b40<br>ab2e47720388fa201e242552f8d8b82363c6c52f6c63fa3fec9dce027cb12e77<br>bc11d036fe59abb3915f736307c56d2fd43e8127e46c31f926eeda864f4d66dc<br>c3f7cea80dbafaa90a88b28a6dfb1227caaf5c2a29f0ce06bf663d6ed2cfc079</p><p>&nbsp;</p><h3>Tenzor SHA-256&nbsp;</h3><p>0580ebf601989457f0708799b431fd4d9f5e59d98838282d72936099aa6636da<br>7a25253e6d8d9ccf62a67f8014cacb301daf9e40f1b68ecc7f354d6896d16960<br>cab7855ccfca19a06eea76e0e170f592dcc95906ecfa5436f5a11947e04e63d5<br>dfbeab30d14df9104a95de83ab4690308c653eb0c3706554687c45a77adc1385</p>