PowerShell ScriptBlockLogging: Disable/Lower Windows Defender Monitoring via Set-MpPreference

title: "PowerShell ScriptBlockLogging: Disable/Lower Windows Defender Monitoring via Set-MpPreference"
id: 84fc32c1-c066-4b72-bd06-c454d023cbcb
related:
  - id: ec19ebab-72dc-40e1-9728-4c0b805d722c
    type: derived
  - id: 14c71865-6cd3-44ae-adaa-1db923fae5f2
    type: derived
status: test
description: This rule flags PowerShell script block activity that calls Set-MpPreference to disable multiple Windows Defender monitoring and scanning features, using parameter values like -Disable* set to true/1. It also triggers when Set-MpPreference is used to set high/low/moderate/severe threat default actions to Allow. Disabling or relaxing Defender protections can help attackers evade detection and response, and the rule relies on Script Block Logging telemetry containing the relevant Set-MpPreference text and parameters.
references:
  - https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1562.001/T1562.001.md
  - https://learn.microsoft.com/en-us/powershell/module/defender/set-mppreference?view=windowsserver2022-ps
  - https://bidouillesecurity.com/disable-windows-defender-in-powershell/
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/powershell/powershell_script/posh_ps_tamper_windows_defender_set_mp.yml
author: frack113, elhoim, Tim Shelton (fps, alias support), Swachchhanda Shrawan Poudel, Nasreddine Bencherchali (Nextron Systems), Huntrule Team
date: 2022-01-16
modified: 2024-01-02
tags:
  - attack.defense-impairment
  - attack.t1685
logsource:
  product: windows
  category: ps_script
  definition: "Requirements: Script Block Logging must be enabled"
detection:
  selection_options_disabling_preference:
    ScriptBlockText|contains: Set-MpPreference
  selection_options_disabling_function:
    ScriptBlockText|contains:
      - -dbaf $true
      - -dbaf 1
      - -dbm $true
      - -dbm 1
      - -dips $true
      - -dips 1
      - -DisableArchiveScanning $true
      - -DisableArchiveScanning 1
      - -DisableBehaviorMonitoring $true
      - -DisableBehaviorMonitoring 1
      - -DisableBlockAtFirstSeen $true
      - -DisableBlockAtFirstSeen 1
      - -DisableCatchupFullScan $true
      - -DisableCatchupFullScan 1
      - -DisableCatchupQuickScan $true
      - -DisableCatchupQuickScan 1
      - -DisableIntrusionPreventionSystem $true
      - -DisableIntrusionPreventionSystem 1
      - -DisableIOAVProtection $true
      - -DisableIOAVProtection 1
      - -DisableRealtimeMonitoring $true
      - -DisableRealtimeMonitoring 1
      - -DisableRemovableDriveScanning $true
      - -DisableRemovableDriveScanning 1
      - -DisableScanningMappedNetworkDrivesForFullScan $true
      - -DisableScanningMappedNetworkDrivesForFullScan 1
      - -DisableScanningNetworkFiles $true
      - -DisableScanningNetworkFiles 1
      - -DisableScriptScanning $true
      - -DisableScriptScanning 1
      - -MAPSReporting $false
      - -MAPSReporting 0
      - -drdsc $true
      - -drdsc 1
      - -drtm $true
      - -drtm 1
      - -dscrptsc $true
      - -dscrptsc 1
      - -dsmndf $true
      - -dsmndf 1
      - -dsnf $true
      - -dsnf 1
      - -dss $true
      - -dss 1
  selection_other_default_actions_allow:
    ScriptBlockText|contains: Set-MpPreference
  selection_other_default_actions_func:
    ScriptBlockText|contains:
      - HighThreatDefaultAction Allow
      - htdefac Allow
      - LowThreatDefaultAction Allow
      - ltdefac Allow
      - ModerateThreatDefaultAction Allow
      - mtdefac Allow
      - SevereThreatDefaultAction Allow
      - stdefac Allow
  condition: all of selection_options_disabling_* or all of selection_other_default_actions_*
falsepositives:
  - Legitimate PowerShell scripts that disable Windows Defender for troubleshooting purposes. Must be investigated.
level: high
license: DRL-1.1