Windows Code Integrity blocks unsigned DLL loads into MpCmdRun.exe and NisSrv.exe

Flags security-mitigations events where MpCmdRun or NisSrv are prevented from loading unsigned DLLs.

FreeReviewedSigma · High · v2

Product: windows
Service: security-mitigations
Author: Bhabesh Raj (SigmaHQ), DRL 1.1
Published: 2022-08-02
Updated: 2026-07-31

ATT&CK techniques

Execution → Defense Evasion

Recon
Resource Dev
Initial Access
Execution
- T1574.001DLL
Persistence
- T1574.001DLL
Priv Esc
- T1574.001DLL
Defense Evasion
- T1574.001DLL
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule flags Code Integrity (CI) enforcement events where Microsoft Defender-related binaries MpCmdRun.exe and NisSrv.exe are blocked from loading unsigned DLLs. Attackers may use unsigned DLL sideloading to run malicious code within trusted processes, so these blocks are a strong indicator of attempted tampering. The detection relies on Windows security-mitigations telemetry with CI block events (Event IDs 11 and 12) that include the blocked process paths.

Reporting behind it

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Malicious dal_keepalives.dll Sideloaded By Signed Binary (via image_load)

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Windows Code Integrity blocks unsigned DLL loads into MpCmdRun.exe and NisSrv.exe

Pivot detection · T1574.001 · 9 related

Changelog

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-defender-blocked-mpcmdrun-and-nissrv-from-loading-unsigned-dlls-0b0ea3cc

title: Windows Code Integrity blocks unsigned DLL loads into MpCmdRun.exe and NisSrv.exe
id: f2b0ba8e-a7f6-4b5f-b3b5-484f4d7a233a
status: test
description: This rule flags Code Integrity (CI) enforcement events where Microsoft Defender-related binaries MpCmdRun.exe and NisSrv.exe are blocked from loading unsigned DLLs. Attackers may use unsigned DLL sideloading to run malicious code within trusted processes, so these blocks are a strong indicator of attempted tampering. The detection relies on Windows security-mitigations telemetry with CI block events (Event IDs 11 and 12) that include the blocked process paths.
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/builtin/security_mitigations/win_security_mitigations_defender_load_unsigned_dll.yml
author: Bhabesh Raj, Huntrule Team
date: 2022-08-02
modified: 2022-09-28
tags:
  - attack.privilege-escalation
  - attack.persistence
  - attack.execution
  - attack.stealth
  - attack.t1574.001
logsource:
  product: windows
  service: security-mitigations
detection:
  selection:
    EventID:
      - 11
      - 12
    ProcessPath|endswith:
      - \MpCmdRun.exe
      - \NisSrv.exe
  condition: selection
falsepositives:
  - Unknown
level: high
license: DRL-1.1
related:
  - id: 0b0ea3cc-99c8-4730-9c53-45deee2a4c86
    type: derived

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