Storm-0408 Malvertising RegAsm C2 Execution
The Storm-0408 malvertising campaign uses RegAsm.exe from the .NET Framework as a living-off-the-land binary for command and control. After the initial dropper from GitHub establishes a foothold, the malware injects code into RegAsm.exe to connect to C2 over TCP ports 15647 or 9000, exfiltrate data, and access DPAPI. This rule looks for RegAsm.exe launched from a temp or user writable path, which is unusual because the legitimate RegAsm is typically in the .NET Framework directory. In plain terms, it catches when a normal-looking system tool is being used from the wrong place to talk to an attacker.
Sigma
