Threats Tagged 'agent tesla - s0331'

Since late March 2026, a large-scale phishing campaign has been deploying malware including Agent Tesla, Remcos, XWorm, and Best Private LOGGER through fileless techniques and low-detection Lua-based loaders. Attackers impersonate well-known companies using business cooperation lures to distribute malicious archives containing obfuscated JavaScript files. These scripts deploy either AutoIt or LuaJIT interpreters alongside disguised scripts masquerading as TrueType Font (.ttf) files. The Lua loaders employ sophisticated anti-analysis techniques including custom ROT ciphers, decoy memory allocation, and Donut shellcode generation for reflective in-memory payload execution. The campaign evolved from simpler implementations in October 2025 to highly complex versions by June 2026, incorporating API unhooking and advanced debugging countermeasures. Victims are ultimately infected with Remote Access Trojans and infostealers that enable full system control and extensive data exfiltration.

A sophisticated phishing campaign was identified distributing multiple malware families through a multi-stage loader utilizing steganography and fileless techniques. The infection chain begins with archive attachments containing files disguised as financial documents, primarily targeting Indian organizations using names related to GST, NEFT, RTGS, and IMPS transactions. The loader employs in-memory execution to avoid disk-based artifacts and uses embedded .NET Bitmap objects to conceal payloads. Various malware families have been deployed including Remcos RAT, Agent Tesla, MassLogger, Phantom Stealer, Dark Cloud, Red Line Stealer, Snake keyloggers, Formbook, and xworm. The final payloads establish persistence through registry Run keys, perform process hollowing, steal browser credentials, record audio and webcam, and exfiltrate data to command-and-control infrastructure. The campaign exhibits characteristics of a loader-as-a-service operation serving multiple threat actors globally.

MediumMalwareBritish Indian Ocean TerritoryIndia#fileless#loader-as-a-service#steganography

This analysis examines new obfuscation techniques employed by Gremlin stealer malware to conceal malicious payloads within embedded resources. A variant protected by sophisticated commercial packing utility uses instruction virtualization, transforming code into custom bytecode executed by a private virtual machine. The malware siphons sensitive information including payment card details, browser cookies, session tokens, cryptocurrency wallet data, and FTP/VPN credentials from compromised systems. It exfiltrates data to attacker-controlled servers at hxxp[:]194.87.92[.]109 for potential publication or sale. Recent iterations incorporate expanded Discord token extraction, active financial fraud through crypto clipper functionality that replaces cryptocurrency wallet addresses in real-time, and WebSocket-based session hijacking to bypass modern cookie protections. The malware employs advanced anti-analysis techniques including XOR-encoded payloads in .NET resource sections, identifier renaming, string encryp...