Homoglyph
Also written confusable
A character that looks identical or near-identical to another but has a different Unicode code point — Cyrillic а for Latin a, Greek ο for o, a full-width or mathematical-italic letterform. Swapping a few of them makes a word visually unchanged to a human and completely different to a string comparison, defeating exact matching and most fuzzy matching too. Defending against them means Unicode confusable-folding as part of normalisation; a related trick uses bidirectional control characters (Trojan Source) to make text render differently from how it parses.
See also obfuscation / encoding · normalization pre-pass · leetspeak
Related terms
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Obfuscation / encoding
Attack concepts
Rewriting a payload so it survives the defence but is still recoverable by the model — base64, hex, ROT13 and Caesar shifts, character or word reversal…
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Normalization pre-pass
MoorAI terms
A bounded decode-and-fold stage that runs before the detectors: strip zero-width and bidirectional control characters, fold homoglyphs and leetspeak…
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Leetspeak
Attack concepts
Substituting digits and symbols for visually similar letters — 3 for e, 1 or ! for i/l, 4 or @ for a, 0 for o — as in h4rm3l. Models read it fluently;
Attack concepts
The mechanisms the families above exploit, plus the agent-specific ones that have no chatbot equivalent. If you only read one entry on this page, read indirect prompt injection.