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
The proof-of-concept uses Rust to load amsi.dll, find the address of AmsiScanBuffer, change memory protection to writable, and patch the function's beginning with a return instruction that sets the result to AMSI_RESULT_CLEAN. This defeats AMSI's ability to scan script content before execution, bypassing detection by endpoint security solutions that rely on AMSI.
Detection & mitigation
Monitor for suspicious memory modifications to amsi.dll, specifically writes to the AmsiScanBuffer function, using endpoint detection and response (EDR) tools with memory integrity monitoring. Mitigate by enabling Windows Defender Application Control (WDAC) or AppLocker to restrict untrusted code execution and keeping AMSI-integrated security products updated.
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.