PowerShell ScriptBlock Logging: Set-MpPreference disables Windows Defender scanning or allows threats

Alert on PowerShell Set-MpPreference usage that disables Defender scanning/monitoring or sets threat default actions to Allow.

FreeReviewedSigma · High · v2

Product: windows
Category: ps_script
Author: frack113, elhoim, Tim Shelton (fps, alias support), Swachchhanda Shrawan Poudel, Nasreddine Bencherchali (Nextron Systems) (SigmaHQ), DRL 1.1
Published: 2022-01-16
Updated: 2026-07-31

Analysis Detection

ATT&CK techniques

Recon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule flags PowerShell script content that calls Set-MpPreference to disable multiple Windows Defender scanning and protection components, such as real-time monitoring and various scanning modes. It also matches attempts to change defender default actions to Allow for different threat severities. Attackers may use these preference changes to reduce detection and prevention while running malicious activity. Telemetry relies on Script Block Logging capturing the ScriptBlockText within PowerShell executions.

Reporting behind it

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PowerShell ScriptBlock Logging: Set-MpPreference disables Windows Defender scanning or allows threats

Pivot detection · T1685 · 9 related

Changelog

v2
Candidate ingested via manual entry.2026-07-31
v1
No changelog recorded for this version.2026-07-30

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

powershell-scriptblocklogging-disable-lower-windows-defender-monitoring-via-set--14c71865

title: "PowerShell ScriptBlock Logging: Set-MpPreference disables Windows Defender scanning or allows threats"
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 content that calls Set-MpPreference to disable multiple Windows Defender scanning and protection components, such as real-time monitoring and various scanning modes. It also matches attempts to change defender default actions to Allow for different threat severities. Attackers may use these preference changes to reduce detection and prevention while running malicious activity. Telemetry relies on Script Block Logging capturing the ScriptBlockText within PowerShell executions.
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

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