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Windows Defender mpclient.dll Side-loading: MpCmdRun.exe or NisSrv.exe from Non-Default Paths

Alerts when MpCmdRun.exe or NisSrv.exe runs from non-default directories, a common indicator of possible mpclient.dll sideloading.

FreeUnreviewedSigmahighv1
title: "Windows Defender mpclient.dll Side-loading: MpCmdRun.exe or NisSrv.exe from Non-Default Paths"
id: 41b51c3b-066f-4ec4-85ab-042e8678bcb6
related:
  - id: 418dc89a-9808-4b87-b1d7-e5ae0cb6effc
    type: similar
  - id: 7002aa10-b8d4-47ae-b5ba-51ab07e228b9
    type: derived
status: test
description: This rule flags executions of Windows Defender binaries MpCmdRun.exe and NisSrv.exe where the process image is outside their expected default installation directories. Attackers can use DLL sideloading to load a malicious mpclient.dll in place of the legitimate dependency, enabling persistence, stealth, or privilege escalation. Telemetry required is process creation data including the full Image path for these Defender executables.
references:
  - https://www.sentinelone.com/blog/living-off-windows-defender-lockbit-ransomware-sideloads-cobalt-strike-through-microsoft-security-tool
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_mpcmdrun_dll_sideload_defender.yml
author: Bhabesh Raj, Huntrule Team
date: 2022-08-01
modified: 2023-08-04
tags:
  - attack.privilege-escalation
  - attack.persistence
  - attack.execution
  - attack.stealth
  - attack.t1574.001
logsource:
  product: windows
  category: process_creation
detection:
  selection:
    Image|endswith:
      - \MpCmdRun.exe
      - \NisSrv.exe
  filter_main_known_locations:
    Image|startswith:
      - C:\Program Files (x86)\Windows Defender\
      - C:\Program Files\Microsoft Security Client\
      - C:\Program Files\Windows Defender\
      - C:\ProgramData\Microsoft\Windows Defender\Platform\
      - C:\Windows\WinSxS\
  condition: selection and not 1 of filter_main_*
falsepositives:
  - Unlikely
level: high
license: DRL-1.1

What it detects

This rule flags executions of Windows Defender binaries MpCmdRun.exe and NisSrv.exe where the process image is outside their expected default installation directories. Attackers can use DLL sideloading to load a malicious mpclient.dll in place of the legitimate dependency, enabling persistence, stealth, or privilege escalation. Telemetry required is process creation data including the full Image path for these Defender executables.

Known false positives

  • Unlikely

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