Sigma rule: PowerShell Defender Threat Severity Default Action Set to 'Allow' or 'NoAction'

Rule

Title

PowerShell Defender Threat Severity Default Action Set to 'Allow' or 'NoAction'

Status

experimental

Level

high

Author

Matt Anderson (Huntress)

Date

2025-07-11

File

rules/windows/process_creation/proc_creation_win_defender_default_action_modified.yml

Commit

ccbb0369507f796db0b0ae6854c8a2be471b9d84

Detects the use of PowerShell to execute the 'Set-MpPreference' cmdlet to configure Windows Defender's threat severity default action to 'Allow' (value '6') or 'NoAction' (value '9').
This is a highly suspicious configuration change that effectively disables Defender's ability to automatically mitigate threats of a certain severity level.
An attacker might use this technique via the command line to bypass defenses before executing payloads.

Log source

product

windows

category

process_creation

Detection

selection_cmdlet:
    CommandLine|contains: 'Set-MpPreference'
selection_action:
    CommandLine|contains:
        - '-LowThreatDefaultAction'
        - '-ModerateThreatDefaultAction'
        - '-HighThreatDefaultAction'
        - '-SevereThreatDefaultAction'
        - '-ltdefac '
        - '-mtdefac '
        - '-htdefac '
        - '-stdefac '
selection_value:
    CommandLine|contains:
        - 'Allow'
        - '6'
        - 'NoAction'
        - '9'
condition: all of selection_*

False positives (as the rule lists them)

• Highly unlikely

Tags

• attack.defense-impairment
• attack.t1685

MITRE ATT&CK ids this rule names

• T1685

Related rules

• 5a9e1b2c-8f7d-4a1e-9b3c-0f6d7e5a4b1f (similar)

References

• https://learn.microsoft.com/en-us/powershell/module/defender/set-mppreference
• https://learn.microsoft.com/en-us/windows-hardware/customize/desktop/unattend/security-malware-windows-defender-threatseveritydefaultaction
• https://research.splunk.com/endpoint/7215831c-8252-4ae3-8d43-db588e82f952
• https://gist.github.com/Dump-GUY/8daef859f382b895ac6fd0cf094555d2
• https://thedfirreport.com/2021/10/18/icedid-to-xinglocker-ransomware-in-24-hours/

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_defender_default_action_modified.yml