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SAST, DAST, IAST, and SCA examine different evidence: code, a running application, instrumented execution, and third-party components. Think of them as inspections at different points in designing and building a car and taking it on the road—not as interchangeable tests or exact automotive equivalents.
What do SAST, DAST, IAST, and SCA mean?
Application security testing is an umbrella term for methods that inspect software from different viewpoints. Some examine code before it runs; others observe an application while it runs or assess the components it uses. The acronym tells you something about the evidence a method can examine, not whether a particular tool finds every issue.
| Method | What it examines | Typical workflow position | Access or setup | Evidence and coverage limit |
|---|---|---|---|---|
| SAST — Static Application Security Testing | Source code or related artifacts without observing the application’s live behavior. | Often early in development; OWASP includes it among commit-time checks. | Access to code or relevant artifacts; it does not require a running application. | Can point developers to code patterns to investigate. It does not provide live runtime evidence. |
| DAST — Dynamic Application Security Testing | A running application, tested from an external perspective. | OWASP lists DAST among deploy-time checks against a running application. | A running target that the testing process can interact with. | Shows how the application responds to external probes; external interaction does not reveal every internal code path. |
| IAST — Interactive Application Security Testing | A running application’s behavior, observed from within as activity exercises it. | During application use or testing; exact timing depends on the workflow. | Instrumentation, commonly an agent inside a supported runtime, plus exercised behavior. | Can combine runtime observations with code and data-flow context. It cannot establish that unexercised paths were tested. |
| SCA — Software Composition Analysis | Third-party libraries or components used by an application, including checks for known vulnerabilities. | OWASP places SCA among build-time checks. | Access to information about the application’s components. | Helps assess component risks; checking components alone does not establish that the application as a whole is secure. |
These are category-level distinctions. Capabilities, supported languages and frameworks, integrations, and finding details vary among tools; the category name by itself does not establish a tool’s performance.
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How does the car analogy work?
Imagine a car being designed, assembled from parts, and driven. The analogy helps explain when different checks look at evidence, but software checks inspect code, dependencies, or application behavior—not physical vehicles. No automotive inspection maps perfectly to a software testing method.
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SAST: review the design and build plans
Reading source code without running the application resembles reviewing plans for a risky design or assembly pattern. The key point is early access to the plans, not evidence of how a completed car behaves on the road.
SCA: inspect the parts list and suppliers
Modern applications use third-party libraries, much as a vehicle is assembled from components. SCA checks those software components, including for known vulnerabilities. A parts-list check is useful, but it does not prove that the complete vehicle—or application—is secure.
DAST: take the assembled car for a road test
DAST interacts with a running application from the outside and observes its responses, like evaluating a finished car through a drive. That external view does not expose every internal code path just because the application is being exercised.
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IAST observes a running application from within as tests or other activity exercise it. OWASP’s DevSecOps Guideline describes it as combining strengths of static and dynamic analysis by instrumenting the running application and observing it from inside while it executes. The analogy’s instrumented drive illustrates that idea; actual IAST coverage depends on which behaviors tests exercise and whether the runtime is supported.
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Where do these checks fit in a development workflow?
OWASP’s Security Testing guidance gives an example of placing checks at different stages. This is a way to organize complementary evidence, not a mandatory schedule for every team or application.
- At commit time: run SAST, secrets scanning, and infrastructure-as-code (IaC) analysis as appropriate. These checks can review code, configuration, and infrastructure definitions early.
- At build time: include SCA and image scanning where relevant. SCA assesses third-party software components.
- At deploy time: use DAST against a running application when appropriate. It tests externally observable behavior.
IAST fits where an application can be instrumented and exercised, often as tests run. Its usefulness depends on the paths those tests actually reach, not merely on installing an agent.
What related checks should not be confused with these acronyms?
Secrets scanning
Secrets scanning looks for exposed sensitive values, such as credentials or API keys, in repositories or configuration. OWASP lists it among commit-time checks. It is related to application security work, but it is not another name for SAST.
Infrastructure as Code analysis
Infrastructure as Code (IaC) describes infrastructure in files or code. Checking those definitions can reveal security issues in the planned setup; OWASP also identifies it as an early, commit-time activity. It complements code and runtime checks rather than replacing them.
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API security testing
APIs are a distinct area of security testing identified in OWASP’s DevSecOps overview. API testing may involve a running service, but the label should not be silently treated as synonymous with DAST: the terms describe different things, and an API test’s method depends on what it actually examines.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How should a team choose which methods to use?
Start with the evidence needed for the risk in question. Code patterns, third-party components, and externally visible runtime behavior are different sources of information; no single acronym covers them all. A combination can provide complementary viewpoints, but no particular set of checks guarantees security.
- Lifecycle timing: Does the check provide useful feedback while code or configuration is being changed, during a build, or against a deployed application?
- Access: Does it need source code, component information, a running target, or instrumentation in the runtime?
- Visibility: Is it examining code, third-party components, external responses, or behavior from inside the application?
- Coverage: For runtime methods, which routes and behaviors do tests actually exercise? For code and component checks, what files or dependencies are in scope?
- Finding context: Does a result provide enough information about the relevant code, component, or observed behavior for a developer to investigate it?
- Integration effort and compatibility: What setup is required, and which languages, frameworks, runtimes, and CI workflows are supported?
OWASP’s IAST comparison discusses factors including timing, visibility, source-code needs, fix guidance, and CI integration effort. These are practical evaluation questions, not universal rankings: category labels alone establish neither accuracy nor false-positive rates, cost, or tool quality.
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