Windows PowerShell sets Microsoft Defender threat severity default actions to Allow/NoAction

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 process creation events where PowerShell runs Set-MpPreference to change Microsoft Defender threat severity default actions to Allow (including value 6) or NoAction (including value 9). Such configuration changes can reduce Defender’s ability to automatically mitigate threats for specified severity levels. The detection relies on command-line telemetry that includes Set-MpPreference and the relevant default-action parameters and values.

Reporting behind it

Related detections9 linkedT1685 — drag to rearrange

Suspicious Vulnerable Intel Ethernet Driver Load for BYOVD via SCATTERED SPIDER (via driver_load)

Malicious Defender Disable And Executable Exclusion Via Registry

Malicious UAC Disable via EnableLUA Registry Modification (via registry_set)

Malicious AMSI and ETW Patching via PowerShell Script

Malicious PowMix AMSI Bypass via amsiInitFailed

Suspicious ThrottleStop Driver Abuse for Defense Evasion in Ransomware Attacks

Malicious Disabling of Microsoft Defender Real-Time Protection via SystemSettingsAdminFlows by DeadLock Ransomware

Suspicious Security Software Uninstallation via WMIC Product Call Uninstall (Chaos Ransomware)

Suspicious Security Product Uninstall via wmic product call uninstall

Windows PowerShell sets Microsoft Defender threat severity default actions to Allow/NoAction

Pivot detection · T1685 · 9 related

Changelog

v2

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.

windows-powershell-set-mppreference-low-moderate-high-severethreatdefaultaction--1e8a9b4d

title: Windows PowerShell sets Microsoft Defender threat severity default actions to Allow/NoAction
id: afd82cfa-d276-45f3-8ea2-5553b02271fc
related:
  - id: 5a9e1b2c-8f7d-4a1e-9b3c-0f6d7e5a4b1f
    type: similar
  - id: 1e8a9b4d-3c2a-4f9b-8d1e-7c6a5b4f3d2e
    type: derived
status: experimental
description: This rule flags process creation events where PowerShell runs Set-MpPreference to change Microsoft Defender threat severity default actions to Allow (including value 6) or NoAction (including value 9). Such configuration changes can reduce Defender’s ability to automatically mitigate threats for specified severity levels. The detection relies on command-line telemetry that includes Set-MpPreference and the relevant default-action parameters and values.
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/
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_defender_default_action_modified.yml
author: Matt Anderson (Huntress), Huntrule Team
date: 2025-07-11
tags:
  - attack.defense-impairment
  - attack.t1685
logsource:
  category: process_creation
  product: windows
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_*
falsepositives:
  - Highly unlikely
level: high
license: DRL-1.1

Convert

This rule as a query you can run. Uses no unlock credit.

SplunkSPL