Core WAF Protection Mechanisms

Core WAF Protection Mechanisms

Understanding how WAFs detect and prevent attacks helps in configuring them effectively. Each protection mechanism addresses specific threat vectors, and combining multiple approaches provides comprehensive coverage.

SQL Injection Protection remains one of the most critical WAF functions. WAFs identify SQL injection attempts by analyzing input parameters for SQL syntax, keywords, and common injection patterns. Advanced WAFs go beyond simple keyword matching to understand SQL grammar and context. For example, detecting the difference between a legitimate surname "O'Brien" and a malicious input "'; DROP TABLE users;--" requires contextual analysis. WAFs can also implement positive security models, allowing only inputs matching expected patterns for each parameter.

Cross-Site Scripting (XSS) Prevention involves detecting and blocking malicious scripts embedded in user inputs. WAFs examine all user-controllable inputs including parameters, headers, and cookies for script tags, event handlers, and obfuscated JavaScript. Modern WAFs must handle various encoding schemes and bypass techniques attackers use. They can also implement Content Security Policy (CSP) headers dynamically, providing browser-level protection against XSS.

Protocol Validation and Request Normalization ensure that incoming requests conform to HTTP standards and application expectations. WAFs validate HTTP methods, header formats, content types, and request structures. They normalize requests by decoding URL encoding, removing null bytes, and standardizing paths to prevent evasion techniques. This normalization process helps other security mechanisms work effectively by ensuring consistent input formats.