Winsage
June 12, 2026
OnyxC2 is a sophisticated credential stealer available for a subscription fee of 0 per month, distributed through disguised lures such as fake Windows updates and legitimate software installers. It functions as a commercial product with features like an automated payload builder, tiered licensing, and a centralized web dashboard. The malware boasts a 99% detection-evasion rate, successfully evading major antivirus solutions during tests. It is developed in C++, utilizing direct system calls and mutating with each build to avoid detection. OnyxC2 collects data from around 210 applications, targeting 45 web browsers, password managers, cryptocurrency wallets, and FTP clients.
The malware is delivered using DLL sideloading, where a password-protected archive contains a legitimate application and a malicious DLL. The attacker's DLL is disguised by inflating its size and is loaded by a trusted binary. The malicious code remains encrypted on disk and decrypts in memory to evade analysis. OnyxC2 communicates with a Cloudflare-fronted command-and-control server to manage infected hosts and execute commands like hardware registration and cookie uploads. The threat extends to business environments, targeting FTP and email clients, with stolen session cookies allowing ongoing access to corporate infrastructure. Implementing anti-data exfiltration controls is recommended as a mitigation strategy.
