Potential Homoglyph Attack Using Lookalike Characters in Filename

Detects the presence of unicode characters which are homoglyphs, or identical in appearance, to ASCII letter characters. This is used as an obfuscation and masquerading techniques. Only "perfect" homoglyphs are included; these are characters that are indistinguishable from ASCII characters and thus may make excellent candidates for homoglyph attack characters.

title: Potential Homoglyph Attack Using Lookalike Characters in Filename
id: 4f1707b1-b50b-45b4-b5a2-3978b5a5d0d6
status: test
description: |
    Detects the presence of unicode characters which are homoglyphs, or identical in appearance, to ASCII letter characters.
    This is used as an obfuscation and masquerading techniques. Only "perfect" homoglyphs are included; these are characters that
    are indistinguishable from ASCII characters and thus may make excellent candidates for homoglyph attack characters.
references:
    - https://redcanary.com/threat-detection-report/threats/socgholish/#threat-socgholish
    - http://www.irongeek.com/homoglyph-attack-generator.php
author: Micah Babinski, @micahbabinski
date: 2023-05-08
tags:
    - attack.stealth
    - attack.t1036
    - attack.t1036.003
logsource:
    category: file_event
    product: windows
detection:
    selection_upper:
        TargetFilename|contains:
            - "\u0410" # А/A
            - "\u0412" # В/B
            - "\u0415" # Е/E
            - "\u041a" # К/K
            - "\u041c" # М/M
            - "\u041d" # Н/H
            - "\u041e" # О/O
            - "\u0420" # Р/P
            - "\u0421" # С/C
            - "\u0422" # Т/T
            - "\u0425" # Х/X
            - "\u0405" # Ѕ/S
            - "\u0406" # І/I
            - "\u0408" # Ј/J
            - "\u04ae" # Ү/Y
            - "\u04c0" # Ӏ/I
            - "\u050C" # Ԍ/G
            - "\u051a" # Ԛ/Q
            - "\u051c" # Ԝ/W
            - "\u0391" # Α/A
            - "\u0392" # Β/B
            - "\u0395" # Ε/E
            - "\u0396" # Ζ/Z
            - "\u0397" # Η/H
            - "\u0399" # Ι/I
            - "\u039a" # Κ/K
            - "\u039c" # Μ/M
            - "\u039d" # Ν/N
            - "\u039f" # Ο/O
            - "\u03a1" # Ρ/P
            - "\u03a4" # Τ/T
            - "\u03a5" # Υ/Y
            - "\u03a7" # Χ/X
    selection_lower:
        TargetFilename|contains:
            - "\u0430" # а/a
            - "\u0435" # е/e
            - "\u043e" # о/o
            - "\u0440" # р/p
            - "\u0441" # с/c
            - "\u0445" # х/x
            - "\u0455" # ѕ/s
            - "\u0456" # і/i
            - "\u04cf" # ӏ/l
            - "\u0458" # ј/j
            - "\u04bb" # һ/h
            - "\u0501" # ԁ/d
            - "\u051b" # ԛ/q
            - "\u051d" # ԝ/w
            - "\u03bf" # ο/o
    condition: 1 of selection_*
falsepositives:
    - File names with legitimate Cyrillic text. Will likely require tuning (or not be usable) in countries where these alphabets are in use.
level: medium

• T1036Masquerading
• T1036.003Rename Legitimate Utilities

• https://redcanary.com/threat-detection-report/threats/socgholish/#threat-socgholish↗
• http://www.irongeek.com/homoglyph-attack-generator.php↗