Potential Homoglyph Attack Using Lookalike Characters in Filename

 1title: Potential Homoglyph Attack Using Lookalike Characters in Filename
 2id: 4f1707b1-b50b-45b4-b5a2-3978b5a5d0d6
 3status: test
 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: 2023/05/08
13tags:
14    - attack.defense_evasion
15    - attack.t1036
16    - attack.t1036.003
17    # - attack.t1036.008
18logsource:
19    category: file_event
20    product: windows
21detection:
22    selection_upper:
23        TargetFilename|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        TargetFilename|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    - File names with legitimate Cyrillic text. Will likely require tuning (or not be usable) in countries where these alphabets are in use.
77level: medium