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Windows MMC Executes Files with RLO-Reversed Extensions in Process Command Line

Alerts when mmc.exe runs with command lines containing RLO-style reversed filename patterns ending in .msc.

FreeReviewedSigma · High · v1
Product
windows
Category
process_creation
Author
Swachchhanda Shrawan Poudel (Nextron Systems) (SigmaHQ), DRL 1.1
Published
2025-02-05
Updated
2026-07-30
AnalysisDetection

ATT&CK techniques

Execution → Defense Evasion

  1. Recon

  2. Resource Dev

  3. Initial Access

  4. Execution

  5. Persistence

  6. Priv Esc

  7. Defense Evasion

  8. Cred Access

  9. Discovery

  10. Lateral Movement

  11. Collection

  12. C2

  13. Exfiltration

  14. Impact

What it detects

This rule flags Windows process creation events where mmc.exe is the image and the command line contains specific reversed-extension filename patterns ending in .msc. Using Right-to-Left Override can cause a file’s displayed extension to appear as a different document type, helping attackers disguise the true target. The detection relies on process creation telemetry including the process image path and the full command line text.

Reporting behind it

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Suspicious Windows Script Host Execution of JavaScript from Temporary Archive Extraction Folder (via process_creation)
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Suspicious Script Interpreter Spawned by OneNote via Embedded Attachment (via process_creation)
Suspicious ClickFix Command Execution via RunMRU Registry Key
Windows MMC Executes Files with RLO-Reversed Extensions in Process Command Line
Pivot detection · T1204.002 · 9 related

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