Sigma rule: Powershell Base64 Encoded MpPreference Cmdlet

A detection rule from the SigmaHQ repository, shown as its author published it. Dataset version ref-1749d91d6592, updated 2023-01-30T00:00:00.000Z.

Rule

Title
Powershell Base64 Encoded MpPreference Cmdlet
Status
test
Level
high
Author
Florian Roth (Nextron Systems)
Date
2022-03-04
Modified
2023-01-30
File
rules/windows/process_creation/proc_creation_win_powershell_base64_mppreference.yml
Commit
ccbb0369507f796db0b0ae6854c8a2be471b9d84

Detects base64 encoded "MpPreference" PowerShell cmdlet code that tries to modifies or tamper with Windows Defender AV

Log source

product
windows
category
process_creation

Detection

selection:
    - CommandLine|base64offset|contains:
          - 'Add-MpPreference '
          - 'Set-MpPreference '
          - 'add-mppreference '
          - 'set-mppreference '
    - CommandLine|contains:
          # UTF16-LE
          - 'QQBkAGQALQBNAHAAUAByAGUAZgBlAHIAZQBuAGMAZQAgA'
          - 'EAZABkAC0ATQBwAFAAcgBlAGYAZQByAGUAbgBjAGUAIA'
          - 'BAGQAZAAtAE0AcABQAHIAZQBmAGUAcgBlAG4AYwBlACAA'
          - 'UwBlAHQALQBNAHAAUAByAGUAZgBlAHIAZQBuAGMAZQAgA'
          - 'MAZQB0AC0ATQBwAFAAcgBlAGYAZQByAGUAbgBjAGUAIA'
          - 'TAGUAdAAtAE0AcABQAHIAZQBmAGUAcgBlAG4AYwBlACAA'
          - 'YQBkAGQALQBtAHAAcAByAGUAZgBlAHIAZQBuAGMAZQAgA'
          - 'EAZABkAC0AbQBwAHAAcgBlAGYAZQByAGUAbgBjAGUAIA'
          - 'hAGQAZAAtAG0AcABwAHIAZQBmAGUAcgBlAG4AYwBlACAA'
          - 'cwBlAHQALQBtAHAAcAByAGUAZgBlAHIAZQBuAGMAZQAgA'
          - 'MAZQB0AC0AbQBwAHAAcgBlAGYAZQByAGUAbgBjAGUAIA'
          - 'zAGUAdAAtAG0AcABwAHIAZQBmAGUAcgBlAG4AYwBlACAA'
condition: selection

False positives (as the rule lists them)

  • Unknown

Tags

  • attack.defense-impairment
  • attack.t1685

MITRE ATT&CK ids this rule names

References

Read on 2026-11-03T00:58:21.399Z under licence sigma-drl-1.1@d5f4c36a from https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules/windows/process_creation/proc_creation_win_powershell_base64_mppreference.yml

Sources and licences

  • SigmaHQ

    "Powershell Base64 Encoded MpPreference Cmdlet" by Florian Roth (Nextron Systems) (SigmaHQ). Rule: https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules/windows/process_creation/proc_creation_win_powershell_base64_mppreference.yml.
    Licensed under the Detection Rule License (DRL) 1.1: https://github.com/SigmaHQ/Detection-Rule-License

    Detection Rule License (DRL) 1.1

Cite this page

Dragons Eye Ransomware Tracker, "Sigma rule: Powershell Base64 Encoded MpPreference Cmdlet",
entity page, dataset version ref-1749d91d6592, updated 2023-01-30T00:00:00.000Z,
https://ransomware-tracker.com/detections/sigma/c6fb44c6-71f5-49e6-9462-1425d328aee3 (accessed 2026-11-03).
Underlying source: SigmaHQ rule c6fb44c6-71f5-49e6-9462-1425d328aee3, commit ccbb0369507f796db0b0ae6854c8a2be471b9d84.

Pages change. The dataset version identifies the data, but no archive of old versions is kept, so this citation cannot be replayed later.