Detection Methodology Comparison

DAST detection relies on pattern matching between requests and responses. Scanners send payloads designed to trigger specific vulnerability classes, then analyze responses for evidence of successful exploitation. For SQL injection, DAST might send quotes and SQL commands, looking for database errors or behavioral changes in responses. This black-box approach requires no knowledge of internal application structure but might miss vulnerabilities that don't produce observable changes.

IAST detection observes actual application behavior during request processing. When applications receive potentially malicious input, IAST sensors track how that input flows through the application. For SQL injection, IAST watches whether user input reaches database queries without proper sanitization. This direct observation eliminates guesswork—IAST knows exactly how applications process data and whether security controls are properly applied.

The methodological differences create distinct detection profiles. DAST excels at finding vulnerabilities with clear external symptoms: error messages, timing differences, or behavioral changes. IAST identifies vulnerabilities regardless of external symptoms by observing internal behavior. A blind SQL injection that returns identical responses might evade DAST detection but stands out clearly to IAST watching database queries being constructed.