SAST vs DAST: Static vs Dynamic Application Security Testing
Overview SAST scans an application’s source code at rest to catch insecure patterns before the app ever runs, while DAST attacks a running application from the outside to find exploitable flaws in its live behavior. Teams use both because each catches vulnerability classes the other structurally cannot see. Comparison Diagram SASTsource code, no executionfunction login(u,p) { const q = "SELECT..+p"; db.exec(q);}reads code, flags line 128e.g. unsanitized SQL concatDASTrunning app, black-boxLive App/login endpointPOST u=' OR 1=1--sends live requests, observes responsee.g. auth bypass returned Comparison Table Aspect SAST DAST What it examines Source code, bytecode, or binaries at rest A running, deployed application from outside Access level White-box — full visibility into code internals Black-box — only sees inputs and outputs like an attacker When in SDLC Early, during coding and in CI on every commit Later, once a build is deployed to a test or staging environment Environment needed None — analyzes files directly, no app needs to run A live, reachable instance of the application Vulnerability classes found Insecure code patterns: SQL string building, hardcoded secrets, unsafe deserialization Exploitable runtime behavior: auth bypass, injection responses, misconfigured headers Language/stack dependency Tied to the language and framework being parsed Language-agnostic — probes over HTTP/HTTPS regardless of stack False positive tendency Higher — flags patterns that may not be reachable or exploitable Lower — findings are confirmed by actual exploit attempts Remediation output Exact file and line number to fix Vulnerable URL, parameter, and request/response evidence Key Differences SAST inspects source code without running it; DAST attacks a live instance without seeing its internals SAST fits early into CI pipelines per-commit; DAST needs a deployed build to test against SAST pinpoints the exact line number; DAST reports the vulnerable endpoint and payload SAST is prone to false positives from unreachable code paths; DAST confirms via actual exploitation SAST misses runtime configuration flaws that DAST catches, like missing security headers or session issues When to Use Each SAST ...