Sigma rule: Tamper Windows Defender - ScriptBlockLogging

Rule

Title

Tamper Windows Defender - ScriptBlockLogging

Status

test

Level

high

Author

frack113, elhoim, Tim Shelton (fps, alias support), Swachchhanda Shrawan Poudel, Nasreddine Bencherchali (Nextron Systems)

Date

2022-01-16

Modified

2024-01-02

File

rules/windows/powershell/powershell_script/posh_ps_tamper_windows_defender_set_mp.yml

Commit

ccbb0369507f796db0b0ae6854c8a2be471b9d84

Detects PowerShell scripts attempting to disable scheduled scanning and other parts of Windows Defender ATP or set default actions to allow.

Log source

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_*

False positives (as the rule lists them)

• Legitimate PowerShell scripts that disable Windows Defender for troubleshooting purposes. Must be investigated.

Tags

• attack.defense-impairment
• attack.t1685

MITRE ATT&CK ids this rule names

• T1685

Related rules

• ec19ebab-72dc-40e1-9728-4c0b805d722c (derived)

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/

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/powershell/powershell_script/posh_ps_tamper_windows_defender_set_mp.yml