Potential Homoglyph Attack Using Lookalike Characters in Filename

Severity: medium
Author: Micah Babinski, @micahbabinski
Source: upstream

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 coverage

Tactic	Techniques
Defense Evasion	`T1036` Masquerading, `T1036.003` Masquerading: Rename Legitimate Utilities

Event coverage

Provider	Event ID	Title
Sysmon	11	FileCreate

Stages and Predicates

Stage 1: `1 of selection_upper`

or:
TargetFilename|contains: 'Α'
TargetFilename|contains: 'Β'
TargetFilename|contains: 'Ε'
TargetFilename|contains: 'Ζ'
TargetFilename|contains: 'Η'
TargetFilename|contains: 'Ι'
TargetFilename|contains: 'Κ'
TargetFilename|contains: 'Μ'
TargetFilename|contains: 'Ν'
TargetFilename|contains: 'Ο'
TargetFilename|contains: 'Ρ'
TargetFilename|contains: 'Τ'
TargetFilename|contains: 'Υ'
TargetFilename|contains: 'Χ'
TargetFilename|contains: 'Ѕ'
TargetFilename|contains: 'І'
TargetFilename|contains: 'Ј'
TargetFilename|contains: 'А'
TargetFilename|contains: 'В'
TargetFilename|contains: 'Е'
TargetFilename|contains: 'К'
TargetFilename|contains: 'М'
TargetFilename|contains: 'Н'
TargetFilename|contains: 'О'
TargetFilename|contains: 'Р'
TargetFilename|contains: 'С'
TargetFilename|contains: 'Т'
TargetFilename|contains: 'Х'
TargetFilename|contains: 'Ү'
TargetFilename|contains: 'Ӏ'
TargetFilename|contains: 'Ԍ'
TargetFilename|contains: 'Ԛ'
TargetFilename|contains: 'Ԝ'

Stage 2: `1 of selection_lower`

or:
TargetFilename|contains: 'ο'
TargetFilename|contains: 'а'
TargetFilename|contains: 'е'
TargetFilename|contains: 'о'
TargetFilename|contains: 'р'
TargetFilename|contains: 'с'
TargetFilename|contains: 'х'
TargetFilename|contains: 'ѕ'
TargetFilename|contains: 'і'
TargetFilename|contains: 'ј'
TargetFilename|contains: 'һ'
TargetFilename|contains: 'ӏ'
TargetFilename|contains: 'ԁ'
TargetFilename|contains: 'ԛ'
TargetFilename|contains: 'ԝ'

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

Field	Kind	Values
`TargetFilename`	match	`Α` `Β` `Ε` `Ζ` `Η` `Ι` `Κ` `Μ` `Ν` `Ο` `Ρ` `Τ` `Υ` `Χ` `ο` `Ѕ` `І` `Ј` `А` `В` `Е` `К` `М` `Н` `О` `Р` `С` `Т` `Х` `а` `е` `о` `р` `с` `х` `ѕ` `і` `ј` `Ү` `һ` `Ӏ` `ӏ` `ԁ` `Ԍ` `Ԛ` `ԛ` `Ԝ` `ԝ`