Threats Tagged 'donut shellcode'

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.

LevelBlue has identified two distinct ValleyRAT attack vectors: campaigns using fake installers and malicious email-based campaigns. Detection volume increased significantly from May 2025, nearly doubling in 2026. The fake installer attacks primarily target Chinese-speaking users and employ advanced techniques including Pool Party Variant 7 process injection and BYOVD methods. The malicious email campaigns target both Chinese and Japanese-speaking users, delivering ZIP archives containing EXE and DLL files that leverage DLL sideloading. The malware employs multiple evasion techniques including junk code insertion, memory size checks, sleeping duration checks, process count validation, and fileless execution using Donut-generated shellcode. ValleyRAT establishes persistence through registry modification and enables remote access capabilities for threat actors.