Understanding Dynamic Application Security Testing

DAST tools operate by sending specially crafted requests to running applications and analyzing responses for security vulnerabilities. This approach mirrors how actual attackers probe applications for weaknesses, making DAST particularly effective at finding exploitable vulnerabilities. The testing process begins with application crawling, where tools automatically discover endpoints, parameters, and functionality by following links and analyzing client-side code.

The attack simulation phase involves sending malicious payloads designed to trigger various vulnerability types. For SQL injection testing, DAST tools inject database metacharacters and commands into input fields, looking for error messages or behavioral changes indicating successful injection. Cross-site scripting tests involve injecting JavaScript payloads and checking whether they execute in response pages. Authentication testing attempts to bypass login mechanisms or escalate privileges through parameter manipulation.

Response analysis represents the most sophisticated aspect of modern DAST tools. Simple string matching has evolved into intelligent pattern recognition that understands application behavior. Tools analyze HTTP response codes, timing variations, content changes, and error messages to identify successful attacks. Machine learning models help distinguish between normal application behavior and indicators of compromise, reducing false positives while improving detection accuracy.