Potential AMSI COM Server Hijacking

Title: Potential AMSI COM Server Hijacking
Status: test
Description:Detects changes to the AMSI come server registry key in order disable AMSI scanning functionalities. When AMSI attempts to starts its COM component, it will query its registered CLSID and return a non-existent COM server. This causes a load failure and prevents any scanning methods from being accessed, ultimately rendering AMSI useless
References:
  -https://enigma0x3.net/2017/07/19/bypassing-amsi-via-com-server-hijacking/
  -https://github.com/r00t-3xp10it/hacking-material-books/blob/43cb1e1932c16ff1f58b755bc9ab6b096046853f/obfuscation/simple_obfuscation.md#amsi-comreg-bypass
Author: Nasreddine Bencherchali (Nextron Systems)
Date: 2023-01-04
modified:2023-08-17
Tags:

• -'attack.defense-impairment'
• -'attack.t1685'

Logsource:

• category: registry_set
• product: windows

Detection:
  selection:
    TargetObject|endswith: '\CLSID\{fdb00e52-a214-4aa1-8fba-4357bb0072ec}\InProcServer32\(Default)'
  filter:
    Details: '%windir%\system32\amsi.dll'
  condition:selection and not filter
Falsepositives:
  -Unknown
Level: high