Windows PowGoop Beacon Decoding — Detection Rule
Detects a DLL decoding and executing the PowGoop config.txt payload, the stage in the MuddyWater infection chain where an obfuscated PowerShell beacon is unwrapped and live C2 communication begins. PowGoop is the primary loader used by MuddyWater (also tracked as SeedWorm, Static Kitten, and MERCURY) and has been their main initial access loader since at least 2020. It abuses DLL side-loading against a fake GoogleUpdate.exe to execute a multi-stage decoding chain, a fully functional PowerShell backdoor disguised with a benign extension. The config.txt contains a hardcoded C2 address and victim GUID, beacons via modified base64-encoded HTTP, and runs C2 traffic under the legitimate Google Update process to evade network detection.