Bypass Record
AMSI Bypass × Microsoft Windows AMSI
A publicly-reported instance of AMSI Bypass bypassing Microsoft Windows AMSI, recorded with its original source. Factual record; no assessment of any specific deployment.
Mechanism
AMSI-Reaper injects code into the memory of AMSI components (e.g., AmsiScanBuffer) to patch or disable them, preventing AMSI from scanning and blocking malicious scripts. The PowerShell version downloads and executes directly in memory; the C# version compiles with CSC and performs the same memory manipulation.
Detection & mitigation
Monitor for suspicious memory modifications to AMSI-related DLLs (e.g., amsi.dll) or unexpected use of CSC.exe to compile and execute C# code. Deploy endpoint detection rules for known AMSI patching patterns and restrict execution policies to signed scripts only.
This is a record of a publicly-reported event, not an assessment of any specific organization's deployment. Detection and mitigation notes are drawn from the cited source. Where the source is silent, fields are omitted.