Sigma rule: Suspicious Process Access of MsMpEng by WerFaultSecure - EDR-Freeze

A detection rule from the SigmaHQ repository, shown as its author published it. Dataset version ref-cd41f99c67c3, updated 2025-11-27T00:00:00.000Z.

Rule

Title
Suspicious Process Access of MsMpEng by WerFaultSecure - EDR-Freeze
Status
experimental
Level
high
Author
Swachchhanda Shrawan Poudel (Nextron Systems)
Date
2025-11-27
File
rules/windows/process_access/proc_access_win_werfaultsecure_msmpeng_access.yml
Commit
ccbb0369507f796db0b0ae6854c8a2be471b9d84

Detects process access events where WerFaultSecure accesses MsMpEng.exe with dbgcore.dll or dbghelp.dll in the call trace, indicating potential EDR freeze techniques.
This technique leverages WerFaultSecure.exe running as a Protected Process Light (PPL) with WinTCB protection level to call MiniDumpWriteDump and suspend EDR/AV processes, allowing malicious activity to execute undetected during the suspension period.

Log source

product
windows
category
process_access
definition
Requires Sysmon Event ID 10 (ProcessAccess) with CallTrace enabled. Example sysmon config snippet with grouping, as logging individual ProcessAccess events can generate excessive logs: <ProcessAccess onmatch="include"> <Rule groupRelation="and"> <TargetImage condition="end with">\MsMpEng.exe</TargetImage> <SourceImage condition="end with">\WerFaultSecure.exe</SourceImage> </Rule> </ProcessAccess>

Detection

selection:
    SourceImage|endswith: '\WerFaultSecure.exe'
    TargetImage|endswith: '\MsMpEng.exe'
    CallTrace|contains:
        - '\dbgcore.dll'
        - '\dbghelp.dll'
condition: selection

False positives (as the rule lists them)

  • Legitimate Windows Error Reporting operations

Tags

  • attack.defense-impairment
  • attack.t1685

MITRE ATT&CK ids this rule names

Related rules

References

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_access/proc_access_win_werfaultsecure_msmpeng_access.yml

Sources and licences

  • SigmaHQ

    "Suspicious Process Access of MsMpEng by WerFaultSecure - EDR-Freeze" by Swachchhanda Shrawan Poudel (Nextron Systems) (SigmaHQ). Rule: https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules/windows/process_access/proc_access_win_werfaultsecure_msmpeng_access.yml.
    Licensed under the Detection Rule License (DRL) 1.1: https://github.com/SigmaHQ/Detection-Rule-License

    Detection Rule License (DRL) 1.1

Cite this page

Dragons Eye Ransomware Tracker, "Sigma rule: Suspicious Process Access of MsMpEng by WerFaultSecure - EDR-Freeze",
entity page, dataset version ref-cd41f99c67c3, updated 2025-11-27T00:00:00.000Z,
https://ransomware-tracker.com/detections/sigma/387df17d-3b04-448f-8669-9e7fd5e5fd8c (accessed 2026-11-03).
Underlying source: SigmaHQ rule 387df17d-3b04-448f-8669-9e7fd5e5fd8c, commit ccbb0369507f796db0b0ae6854c8a2be471b9d84.

Pages change. The dataset version identifies the data, but no archive of old versions is kept, so this citation cannot be replayed later.