Character Substitution Obfuscation in Web Request

Darshan Thummar@Mighty

•updated Jun 11, 2026•0•0•4

This rule detects character substitution obfuscation in web requests, specifically looking for three or more consecutive occurrences of URL-encoded characters that represent common path or null byte characters (e.g., '%5C' for '\', '%2F' for '/', '%00' for null, '%0A' for newline, '%0D' for carriage return). This pattern is often used by attackers to bypass security filters or to obscure malicious payloads in HTTP URIs.