SAST vs DAST
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SAST and DAST are two complementary approaches to testing applications for security flaws. SAST reads the code without running it; DAST attacks the running application from the outside. Each sees what the other cannot, which is exactly why mature application security programs use both rather than arguing over which is better.
How do they differ?#
| SAST (static) | DAST (dynamic) | |
|---|---|---|
| Tests | Source/binary, not running | The running application |
| Perspective | Inside the code | Outside, like an attacker |
| Finds early | Yes — in development | Later — needs a running app |
| Pinpoints code | Yes | No (finds behavior) |
| False positives | More | Fewer, but less coverage of code paths |
| Misses | Runtime/config issues | Deep logic in unexercised code |
SAST shines at catching injection patterns and insecure code early, pointing to the exact line. DAST confirms what is actually exploitable in the deployed app, including misconfiguration that source analysis cannot see.
Why use both (plus more)?#
Because their blind spots are complementary. SAST finds a risky code pattern that may or may not be reachable; DAST proves an endpoint is exploitable but cannot tell you which line to fix. Add software composition analysis for vulnerable dependencies, and you cover code, behavior, and third-party risk together.
SAST and DAST are core secure-development tools. More at the Defense & Hardening hub.
Frequently asked questions#
What is the difference between SAST and DAST?
SAST (Static Application Security Testing) analyzes source code or binaries without running them, finding flaws like injection patterns early in development. DAST (Dynamic Application Security Testing) tests the running application from the outside, like an attacker, finding runtime and configuration issues. Static looks inside the code; dynamic tests real behavior.
Do you need both SAST and DAST?
Yes — they find different things. SAST catches issues early and points to the exact code, but produces false positives and misses runtime/configuration flaws. DAST finds real, exploitable issues in the running app but later and with less code-level detail. Together with dependency scanning, they give fuller coverage than either alone.