Windows Process Creation: MpCmdRun.exe Removing All Windows Defender Definitions

Flags MpCmdRun.exe launched to remove all Windows Defender definition files.

FreeReviewedSigma · High · v1

Product: windows
Category: process_creation
Author: frack113 (SigmaHQ), DRL 1.1
Published: 2021-07-07
Updated: 2026-07-30

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 identifies process creation events where MpCmdRun.exe is launched with arguments that remove all Windows Defender definition files. Attackers may impair defenses by deleting security definition data to reduce detection coverage before or during malicious activity. The detection relies on process creation telemetry, matching MpCmdRun.exe execution via both image attributes and command-line parameters for -RemoveDefinitions and -All.

Reporting behind it

Related detections9 linkedT1685 — drag to rearrange

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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

Windows Process Creation: MpCmdRun.exe Removing All Windows Defender Definitions

Pivot detection · T1685 · 9 related

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

windows-process-creation-mpcmdrun-exe-removing-all-windows-defender-definitions-9719a8aa

title: "Windows Process Creation: MpCmdRun.exe Removing All Windows Defender Definitions"
id: ba192ea6-4088-4854-93c4-fb747554ff5c
status: test
description: This rule identifies process creation events where MpCmdRun.exe is launched with arguments that remove all Windows Defender definition files. Attackers may impair defenses by deleting security definition data to reduce detection coverage before or during malicious activity. The detection relies on process creation telemetry, matching MpCmdRun.exe execution via both image attributes and command-line parameters for -RemoveDefinitions and -All.
references:
  - https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1562.001/T1562.001.md
  - https://unit42.paloaltonetworks.com/unit42-gorgon-group-slithering-nation-state-cybercrime/
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_mpcmdrun_remove_windows_defender_definition.yml
author: frack113, Huntrule Team
date: 2021-07-07
modified: 2023-07-18
tags:
  - attack.defense-impairment
  - attack.t1685
logsource:
  category: process_creation
  product: windows
detection:
  selection_img:
    - Image|endswith: \MpCmdRun.exe
    - OriginalFileName: MpCmdRun.exe
  selection_cli:
    CommandLine|contains|all:
      - " -RemoveDefinitions"
      - " -All"
  condition: all of selection_*
falsepositives:
  - Unknown
level: high
license: DRL-1.1
related:
  - id: 9719a8aa-401c-41af-8108-ced7ec9cd75c
    type: derived

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