SAST vs DAST: What's the Difference?

SAST and DAST are the two most commonly referenced automated application security testing methods, and they're often mentioned together as if they're interchangeable options. They're not options — they test different things, at different stages, and catch different categories of vulnerability. Most serious testing programs need both.

What SAST is

Static Application Security Testing analyzes source code, bytecode or binaries without executing the application. It looks at the code itself, checking for insecure patterns — hardcoded secrets, known-vulnerable code constructs, missing input validation — the way a very thorough, automated code reviewer would.

When it runs: Early — often directly in the developer's editor or in CI, before code is even merged.

What it's good at: Catching issues at the source, before they ship. Finding hardcoded secrets, insecure coding patterns, and known-bad function usage.

What it's weak at: Runtime behavior, configuration issues, and anything that only manifests when the application is actually running — SAST has no visibility into the deployed environment.

What DAST is

Dynamic Application Security Testing tests a running application from the outside, the way an actual attacker would — sending real requests, observing real responses, without access to the source code.

When it runs: Against a deployed, running instance of the application — staging or production.

What it's good at: Finding runtime and configuration issues — misconfigured headers, exposed endpoints, injection points, authentication flaws — that only show up when the application is actually executing.

What it's weak at: Pinpointing the exact location in source code that caused the issue (it sees the symptom, not the code), and testing paths that aren't easily reachable through normal application traffic.

Side-by-side

Why the distinction matters practically

Teams sometimes run one and assume it provides comprehensive coverage. It doesn't. SAST can flag an insecure code pattern that never actually gets triggered in the deployed configuration; DAST can find a real, exploitable issue but can't tell you which line of code caused it. Used together, they cover more of the actual risk than either does alone — and they catch different things even when analyzing the exact same application.

Where each fits in a development workflow

SAST fits naturally into the developer workflow itself — running in CI on every pull request, or even in the editor as code is written, catching issues before they're merged.

DAST fits later, against a deployed environment — staging as part of a release pipeline, or production on a recurring schedule — because it needs something actually running to test against.

What neither one catches well

Both SAST and DAST are automated, pattern- and behavior-based tools. Neither is well suited to finding business logic flaws or access control issues that require understanding what the application is supposed to do — that's where manual testing remains necessary, regardless of how thorough the automated layer is.

How does Averto fit in?

Averto's continuous testing incorporates dynamic testing against the running application, layered with verification that treats findings by real exploitability rather than raw pattern matches — complementing whatever static analysis your team already runs in CI, so coverage spans both the code and the deployed application.