SAST and DAST are complementary classes of application security testing. SAST examines the internals of an application to uncover flaws in the code. DAST evaluates a running application from the outside to find vulnerabilities at the interface. Both are necessary, yet they approach risk from very different directions.
Quick comparison
| Aspect | Static Application Security Testing (SAST) | Dynamic Application Security Testing (DAST) |
|---|---|---|
| Testing model | White-box | Black-box |
| Prerequisites | Access to source code | Deployed, functional application |
| SDLC timing | Early in development | Later in development or pre-release |
| Typical findings | Easy-to-fix bugs and code vulnerabilities | Runtime and exposure-based vulnerabilities |
| Blind spots | Cannot see runtime issues | Cannot see source-level issues |
| Scope | Works for many codebases and app types | Primarily web apps and services |
What is static application security testing
SAST tools require access to source code and perform white-box analysis. They scan non-running code to pinpoint flaws such as numerical errors, race conditions, and directory traversal risks. Because the code is not executed, SAST can produce false positives, yet it remains highly effective at catching issues early in the lifecycle. Agile and DevOps teams rely on SAST to tighten feedback loops and keep security defects from reaching later stages. SAST focuses on code quality and security properties, not on the application’s external behavior.
What is dynamic application security testing
DAST tools operate against a running application using a black-box model. They discover exploitable conditions such as SQL injection, cross-site scripting, and broken authentication. By exercising real requests and responses, DAST offers a third-party perspective that mirrors how an attacker would probe the system. Since DAST needs a functional build, it is most impactful toward the end of the lifecycle or in staging. Findings at this stage can be critical and may require new deployment cycles to remediate.
Using SAST and DAST together: IAST
Interactive Application Security Testing, or IAST, blends insights from SAST and DAST to connect code paths with runtime behavior. Teams often simulate specific environments, data flows, and scenarios to observe how design and implementation choices affect live security outcomes. Combining the approaches reduces false positives and shortens investigation time, which suits agile and DevOps practices.
Other application security testing tools
Vulnerability scanners
Closely related to DAST, vulnerability scanning covers a broader surface, bringing together dynamic checks with assessments across applications, networks, and websites. DAST is best viewed as one component within a scanner’s wider capability set.
Penetration testing tools
Some DAST products include penetration testing features, although penetration testing is a distinct activity. Pen tests validate exploitability at points of access and assess controls such as firewalls, ports, and servers against realistic attack chains.
RASP tools
Runtime application self-protection, or RASP, runs within the application and observes behavior at the operating system level. RASP detects incidents as they happen and alerts security teams, adding in-process protection that complements SAST and DAST.
Static analysis tools
General static analysis resembles SAST and can extend beyond security. Many products pair security checks with capabilities such as abstract interpretation, data-flow analysis, and logic analysis to improve overall code health.
Key takeaways
Use SAST early to prevent code-level flaws from shipping. Use DAST on running builds to find exposure and misconfiguration. Combine both through IAST to link findings to real execution. Enhance coverage with vulnerability scanning, targeted penetration testing, RASP for in-process protection, and broader static analysis for code quality.