A sophisticated Python-based information stealer named XillenStealer has emerged as a significant threat to Windows users, designed to harvest sensitive system data, browser credentials, and cryptocurrency wallet information.
XillenStealer operates through a comprehensive builder framework called “XillenStealer Builder V3.0,” featuring a Python-based Tkinter GUI that enables threat actors to configure and customize their attacks with minimal technical expertise.
The builder includes password authentication via SHA-256 hash validation and allows operators to configure exfiltration channels through Telegram bot integration.
The malware’s modular design enables selective targeting of specific applications and services, including Discord, Steam, cryptocurrency wallets, Telegram sessions, and gaming launchers.
Security researchers at Cyfirma have identified this open-source malware as publicly available on GitHub, making it easily accessible to cybercriminals of varying skill levels.
This flexibility allows attackers to tailor their campaigns based on specific victim profiles or organizational targets.
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Sophisticated Evasion
XillenStealer incorporates multiple layers of anti-analysis and sandbox evasion techniques to avoid detection.
The malware performs comprehensive checks against virtualization environments by identifying VM MAC prefixes, suspicious manufacturer identifiers (VMware, VirtualBox, QEMU), debugging processes, and sandbox-related drivers like vboxguest.sys.
For persistence, the stealer establishes scheduled tasks on Windows systems under the disguise of “System Maintenance Task” or creates cron jobs on Linux systems, ensuring execution upon system reboot.
The malware also attempts process injection into legitimate Windows processes like explorer.exe, though this particular implementation may have limited success due to technical limitations.
GitHub resources abused for malware activities including exfiltration, payload delivery, and command and control (C2) functions
Comprehensive Data Harvesting Capabilities
The stealer’s data collection capabilities are extensive and systematically designed. XillenStealer targets browser-stored credentials from Chromium-based browsers (Chrome, Edge, Brave, Vivaldi, Opera) and Firefox by directly accessing Login Data and History SQLite databases.
The malware uses sophisticated decryption routines to recover plaintext credentials from encrypted browser storage.
Beyond browser data, XillenStealer specifically targets cryptocurrency wallets including Exodus, AtomicWallet, Coinomi, and Electrum, extracting private keys and wallet files.
The malware also harvests Discord authentication tokens, Steam credentials, Telegram session files, and gaming launcher configurations, creating a comprehensive profile of victim activities.
Benefits of Python in cybersecurity include simplification of debugging, powering automation, accelerating development, and its open-source nature
Data exfiltration occurs through Telegram bot integration, with the malware generating both HTML and text reports containing identical stolen information.
The HTML report provides a structured, web-based panel for organized viewing, while the text version offers plain-text accessibility for threat actors.
To handle large data volumes, XillenStealer includes a file-splitting function that breaks oversized archives into segments smaller than 45MB for reliable Telegram transmission.
Each segment is automatically uploaded with identifying captions and removed from the victim’s system after successful transmission.
Security researchers have attributed XillenStealer to Russian-speaking threat actors operating under the “Xillen Killers” brand. The malware was discovered on GitHub under the user account “BengaminButton,” with UI text and code comments written in Russian, strongly indicating Russian-speaking developers.
The threat actor behind BengaminButton claims to be a 15-year-old full-stack developer and penetration tester with expertise across multiple programming languages. The group operates a centralized forum at xillenkillers[.]ru, offering various offensive tools including DDoS platforms, exploitation frameworks, and network attack utilities.
Implications for Organizations
The open-source availability of XillenStealer significantly lowers the barrier to entry for cybercriminals, enabling even low-skilled actors to deploy sophisticated information-stealing campaigns.
The malware’s cross-platform capabilities, combined with its modular design and professional builder interface, represent a concerning evolution in commodity malware distribution.
Organizations should implement comprehensive endpoint detection and response solutions capable of identifying process injection attempts, unusual browser database access patterns, and unauthorized network communications to Telegram services.
Regular security awareness training focusing on the risks of downloading software from unofficial sources remains critical for preventing initial infections.
The discovery of XillenStealer highlights the continued professionalization of cybercrime ecosystems, where threat actors operate structured, service-oriented criminal enterprises with customer support, technical documentation, and subscription-based monetization models.
This trend suggests that information-stealing malware will continue to evolve in sophistication while becoming more accessible to a broader range of cybercriminal actors.
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