Sigma rule: MMC Executing Files with Reversed Extensions Using RTLO Abuse

A detection rule from the SigmaHQ repository, shown as its author published it. Dataset version ref-ecea7aabd880, updated 2025-02-05T00:00:00.000Z.

Rule

Title
MMC Executing Files with Reversed Extensions Using RTLO Abuse
Status
experimental
Level
high
Author
Swachchhanda Shrawan Poudel (Nextron Systems)
Date
2025-02-05
File
rules/windows/process_creation/proc_creation_win_mmc_rlo_abuse_pattern.yml
Commit
ccbb0369507f796db0b0ae6854c8a2be471b9d84

Detects malicious behavior where the MMC utility (`mmc.exe`) executes files with reversed extensions caused by Right-to-Left Override (RLO) abuse, disguising them as document formats.

Log source

product
windows
category
process_creation

Detection

selection_image:
    - Image|endswith: '\mmc.exe'
    - OriginalFileName: 'MMC.exe'
selection_commandline:
    CommandLine|contains: # While looking at these files the prefix of their name will look something like csm.pdf, but in reality it is msc file
        - 'cod.msc'  # Reversed `.doc`
        - 'fdp.msc'  # Reversed `.pdf`
        - 'ftr.msc'  # Reversed `.rtf`
        - 'lmth.msc'  # Reversed `.html`
        - 'slx.msc'  # Reversed `.xls`
        - 'tdo.msc'  # Reversed `.odt`
        - 'xcod.msc'  # Reversed `.docx`
        - 'xslx.msc'  # Reversed `.xlsx`
        - 'xtpp.msc'  # Reversed `.pptx`
condition: all of selection_*

False positives (as the rule lists them)

  • Legitimate administrative actions using MMC to execute misnamed `.msc` files.
  • Unconventional but non-malicious usage of RLO or reversed extensions.

Tags

  • attack.execution
  • attack.stealth
  • attack.t1204.002
  • attack.t1218.014
  • attack.t1036.002

MITRE ATT&CK ids this rule names

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_creation/proc_creation_win_mmc_rlo_abuse_pattern.yml

Sources and licences

  • SigmaHQ

    "MMC Executing Files with Reversed Extensions Using RTLO Abuse" by Swachchhanda Shrawan Poudel (Nextron Systems) (SigmaHQ). Rule: https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules/windows/process_creation/proc_creation_win_mmc_rlo_abuse_pattern.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: MMC Executing Files with Reversed Extensions Using RTLO Abuse",
entity page, dataset version ref-ecea7aabd880, updated 2025-02-05T00:00:00.000Z,
https://ransomware-tracker.com/detections/sigma/9cfe4b27-1e56-48b4-b7a8-d46851c91a44 (accessed 2026-11-03).
Underlying source: SigmaHQ rule 9cfe4b27-1e56-48b4-b7a8-d46851c91a44, 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.