Potential Homoglyph Attack Using Lookalike Characters

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.

Sigma rule (View on GitHub)

 1title: Potential Homoglyph Attack Using Lookalike Characters
 2id: 32e280f1-8ad4-46ef-9e80-910657611fbc
 3status: experimental
 4description: |
 5    Detects the presence of unicode characters which are homoglyphs, or identical in appearance, to ASCII letter characters.
 6    This is used as an obfuscation and masquerading techniques. Only "perfect" homoglyphs are included; these are characters that
 7    are indistinguishable from ASCII characters and thus may make excellent candidates for homoglyph attack characters.    
 8references:
 9    - https://redcanary.com/threat-detection-report/threats/socgholish/#threat-socgholish
10    - http://www.irongeek.com/homoglyph-attack-generator.php
11author: Micah Babinski, @micahbabinski
12date: 2023/05/07
13tags:
14    - attack.defense_evasion
15    - attack.t1036
16    - attack.t1036.003
17   # - attack.t1036.008
18logsource:
19    category: process_creation
20    product: windows
21detection:
22    selection_upper:
23        CommandLine|contains:
24            - "\u0410" # А/A
25            - "\u0412" # В/B
26            - "\u0415" # Е/E
27            - "\u041a" # К/K
28            - "\u041c" # М/M
29            - "\u041d" # Н/H
30            - "\u041e" # О/O
31            - "\u0420" # Р/P
32            - "\u0421" # С/C
33            - "\u0422" # Т/T
34            - "\u0425" # Х/X
35            - "\u0405" # Ѕ/S
36            - "\u0406" # І/I
37            - "\u0408" # Ј/J
38            - "\u04ae" # Ү/Y
39            - "\u04c0" # Ӏ/I
40            - "\u050C" # Ԍ/G
41            - "\u051a" # Ԛ/Q
42            - "\u051c" # Ԝ/W
43            - "\u0391" # Α/A
44            - "\u0392" # Β/B
45            - "\u0395" # Ε/E
46            - "\u0396" # Ζ/Z
47            - "\u0397" # Η/H
48            - "\u0399" # Ι/I
49            - "\u039a" # Κ/K
50            - "\u039c" # Μ/M
51            - "\u039d" # Ν/N
52            - "\u039f" # Ο/O
53            - "\u03a1" # Ρ/P
54            - "\u03a4" # Τ/T
55            - "\u03a5" # Υ/Y
56            - "\u03a7" # Χ/X
57    selection_lower:
58        CommandLine|contains:
59            - "\u0430" # а/a
60            - "\u0435" # е/e
61            - "\u043e" # о/o
62            - "\u0440" # р/p
63            - "\u0441" # с/c
64            - "\u0445" # х/x
65            - "\u0455" # ѕ/s
66            - "\u0456" # і/i
67            - "\u04cf" # ӏ/l
68            - "\u0458" # ј/j
69            - "\u04bb" # һ/h
70            - "\u0501" # ԁ/d
71            - "\u051b" # ԛ/q
72            - "\u051d" # ԝ/w
73            - "\u03bf" # ο/o
74    condition: 1 of selection_*
75falsepositives:
76    - Commandlines with legitimate Cyrillic text; will likely require tuning (or not be usable) in countries where these alphabets are in use.
77level: medium

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