huntrule

PowerShell Base64 Encoded MpPreference Command Lines for Windows Defender Modification

Detects PowerShell Base64 command lines referencing Add-MpPreference/Set-MpPreference to modify Microsoft Defender AV settings.

FreeReviewedSigma · High · v1
Product
windows
Category
process_creation
Author
Florian Roth (Nextron Systems) (SigmaHQ), DRL 1.1
Published
2022-03-04
Updated
2026-07-30
AnalysisDetection

ATT&CK techniques

  1. Recon

  2. Resource Dev

  3. Initial Access

  4. Execution

  5. Persistence

  6. Priv Esc

  7. Defense Evasion

  8. Cred Access

  9. Discovery

  10. Lateral Movement

  11. Collection

  12. C2

  13. Exfiltration

  14. Impact

What it detects

This rule flags process creation events where the PowerShell command line contains Base64-encoded text referencing Add-MpPreference or Set-MpPreference. These cmdlets are used to change Microsoft Defender AV settings, which can be leveraged for defense impairment by altering security configurations. Detection relies on process command-line telemetry, matching either plain Add/Set-MpPreference strings or specific Base64 substrings consistent with UTF-16LE encoding of those cmdlets and related parameters.

Reporting behind it

Related detections9 linkedT1685 — drag to rearrange
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Suspicious In-Memory PowerShell Execution from Web Server via Automation Assembly (via image_load)
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Malicious Zemana Vulnerable Driver Load for EDR Termination (via image_load)
Suspicious EDRKillShifter Vulnerable Driver Load from User Temp Directory (via image_load)
Malicious AuKill EDR Killer Kernel Driver Load via Process Explorer Driver (via image_load)
Malicious FIN7 AvNeutralizer EDR Killer Execution via Masqueraded Binary (via process_creation)
PowerShell Base64 Encoded MpPreference Command Lines for Windows Defender Modification
Pivot detection · T1685 · 9 related

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.