title: MMC Executing Files with Reversed Extensions Using RTLO Abuse
id: 9cfe4b27-1e56-48b4-b7a8-d46851c91a44
status: experimental
description: 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.
references:
    - https://www.unicode.org/versions/Unicode5.2.0/ch02.pdf
    - https://en.wikipedia.org/wiki/Right-to-left_override
    - https://tria.ge/241015-l98snsyeje/behavioral2
author: Swachchhanda Shrawan Poudel (Nextron Systems)
date: 2025-02-05
tags:
    - attack.execution
    - attack.stealth
    - attack.t1204.002
    - attack.t1218.014
    - attack.t1036.002
logsource:
    category: process_creation
    product: windows
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_*
falsepositives:
    - Legitimate administrative actions using MMC to execute misnamed `.msc` files.
    - Unconventional but non-malicious usage of RLO or reversed extensions.
level: high

title: Potential Defense Evasion Via Right-to-Left Override
id: ad691d92-15f2-4181-9aa4-723c74f9ddc3
related:
    - id: e0552b19-5a83-4222-b141-b36184bb8d79
      type: derived
    - id: 584bca0f-3608-4402-80fd-4075ff6072e3
      type: derived
status: test
description: |
    Detects the presence of the "u202+E" character, which causes a terminal, browser, or operating system to render text in a right-to-left sequence.
    This character is used as an obfuscation and masquerading techniques by adversaries to trick users into opening malicious files.
references:
    - https://redcanary.com/blog/right-to-left-override/
    - https://www.malwarebytes.com/blog/news/2014/01/the-rtlo-method
    - https://unicode-explorer.com/c/202E
    - https://tria.ge/241015-l98snsyeje/behavioral2
    - https://unprotect.it/technique/right-to-left-override-rlo-extension-spoofing/
author: Micah Babinski, @micahbabinski, Swachchhanda Shrawan Poudel (Nextron Systems), Luc Génaux
date: 2023-02-15
modified: 2026-03-20
tags:
    - attack.stealth
    - attack.t1036.002
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        CommandLine|contains:
            - '\u202e'  # Unicode RTLO character
            - '[U+202E]'
            # Real char U+202E copied/pasted below
            - '‮'
    condition: selection
falsepositives:
    - Commandlines that contains scriptures such as arabic or hebrew might make use of this character
level: high
regression_tests_path: regression_data/rules/windows/process_creation/proc_creation_win_susp_right_to_left_override/info.yml

title: Potential File Extension Spoofing Using Right-to-Left Override
id: 979baf41-ca44-4540-9d0c-4fcef3b5a3a4
related:
    - id: ad691d92-15f2-4181-9aa4-723c74f9ddc3
      type: derived
status: test
description: |
    Detects suspicious filenames that contain a right-to-left override character and a potentially spoofed file extensions.
references:
    - https://redcanary.com/blog/right-to-left-override/
    - https://www.malwarebytes.com/blog/news/2014/01/the-rtlo-method
    - https://tria.ge/241015-l98snsyeje/behavioral2
    - https://www.unicode.org/versions/Unicode5.2.0/ch02.pdf
author: Jonathan Peters (Nextron Systems), Florian Roth (Nextron Systems), Swachchhanda Shrawan Poudel (Nextron Systems)
date: 2024-11-17
modified: 2026-03-20
tags:
    - attack.execution
    - attack.stealth
    - attack.t1036.002
logsource:
    category: file_event
    product: windows
detection:
    selection_rtlo_unicode:
        TargetFilename|contains:
            - '\u202e'  # Unicode RTLO character
            - '[U+202E]'
            # Real char U+202E copied/pasted below
            - '‮'
    selection_extensions:
        TargetFilename|contains:
            - '3pm.'  # Reversed `.mp3`
            - '4pm.'  # Reversed `.mp4`
            - 'cod.'  # Reversed `.doc`
            - 'fdp.'  # Reversed `.pdf`
            - 'ftr.'  # Reversed `.rtf`
            - 'gepj.'  # Reversed `.jpeg`
            - 'gnp.'  # Reversed `.png`
            - 'gpj.'  # Reversed `.jpg`
            - 'ism.'  # Reversed `.msi`
            - 'lmth.'  # Reversed `.html`
            - 'nls.' # Reversed `.sln`
            - 'piz.'  # Reversed `.zip`
            - 'slx.'  # Reversed `.xls`
            - 'tdo.'  # Reversed `.odt`
            - 'vsc.'  # Reversed `.csv`
            - 'vwm.'  # Reversed `.wmv`
            - 'xcod.'  # Reversed `.docx`
            - 'xslx.'  # Reversed `.xlsx`
            - 'xtpp.'  # Reversed `.pptx`
    condition: all of selection_*
falsepositives:
    - Filenames that contains scriptures such as arabic or hebrew might make use of this character
level: high
regression_tests_path: regression_data/rules/windows/file/file_event/file_event_win_susp_right_to_left_override_extension_spoofing/info.yml