Executive Summary
Unit 42 has identified C2Agent, a new Windows-based malware family written in Go that represents an evolution in 'Living-off-the-AI' (LOTAI) tradecraft. First observed in September 2026, the malware has undergone rapid development, releasing 19 code revisions in under a month. It distinguishes itself by using AI to drive its core tool loop, where an LLM is given interactive control of the host to perform tasks like credential dumping, data exfiltration, and Active Directory reconnaissance.
The attack chain involves a multi-stage delivery process, starting with a Go-based stager that downloads the main C2Agent binary, often masquerading as 'copilot.txt'. The malware leverages legitimate AI services, such as Firecrawl's public MCP server, to perform web scraping and search tasks, effectively blending malicious activity with trusted AI traffic. Recent versions (v2.4) have added advanced capabilities including self-upgrading and the execution of Cobalt Strike Beacon Object Files (BOFs).
C2Agent's impact is significant due to its ability to dynamically extend capabilities via skill-based prompts and MCP servers assigned from the C2 server without needing to redeploy the agent. Furthermore, its network pivoting capabilities allow operators to tunnel traffic through infected hosts into internal networks, posing a severe threat to enterprise security.