sigmamediumHunting

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.

MITRE ATT&CK

T1036 T1036.003

defense-evasion

Detection Query

selection_upper:
  TargetFilename|contains:
    - А
    - В
    - Е
    - К
    - М
    - Н
    - О
    - Р
    - С
    - Т
    - Х
    - Ѕ
    - І
    - Ј
    - Ү
    - Ӏ
    - Ԍ
    - Ԛ
    - Ԝ
    - Α
    - Β
    - Ε
    - Ζ
    - Η
    - Ι
    - Κ
    - Μ
    - Ν
    - Ο
    - Ρ
    - Τ
    - Υ
    - Χ
selection_lower:
  TargetFilename|contains:
    - а
    - е
    - о
    - р
    - с
    - х
    - ѕ
    - і
    - ӏ
    - ј
    - һ
    - ԁ
    - ԛ
    - ԝ
    - ο
condition: 1 of selection_*

Author

Micah Babinski, @micahbabinski

Created

2023-05-08

Data Sources

windowsFile Events

Platforms

windows

References

Tags

attack.defense-evasionattack.t1036attack.t1036.003

Raw Content

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.defense-evasion
    - attack.t1036
    - attack.t1036.003
    # - attack.t1036.008
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