Insights · Application security guide

DAST vs SAST: what each finds, what each misses

SAST analyses your source code without running it, while DAST attacks the running application from the outside. They find different problems, so most teams need both, plus dependency scanning, and a human tester for what automation cannot judge.

Updated: 6 November 2026

The short version

Static application security testing (SAST) reads source code, bytecode or binaries and looks for dangerous patterns before the program runs. Dynamic application security testing (DAST) sends crafted requests to a running application or API and watches how it responds, the way an outside attacker would.

Two related terms complete the picture. Software composition analysis (SCA) inventories your third-party libraries and matches them against known vulnerabilities. Interactive application security testing (IAST) places an agent inside the running application during functional tests and observes data flows from within. The OWASP DevSecOps Guideline lists all four as building blocks of a security pipeline and says teams can adopt and customise the steps gradually, so you do not need everything on day one.

What SAST finds and misses

According to OWASP's overview of source code analysis tools, SAST scales well, can run on every build, points developers to the exact file and line, and can run inside the IDE so issues surface early. It reliably flags well-understood flaw classes such as SQL injection.

OWASP also names the weak spots: a high number of false positives, only a relatively small share of all application security flaws being caught, difficulty with authentication, access control and cryptography problems, and blindness to settings that live outside the code. It is also hard to tell from a report alone whether a finding is actually exploitable.

• Strong at: injection patterns, hard-coded secrets, unsafe API usage, coding-standard violations
• Weak at: runtime configuration, business logic, broken access control, issues that only appear when components interact
• Needs: access to the code and a build that the tool can understand

What DAST finds and misses

OWASP describes web vulnerability scanners as tools that test an application, usually from the outside, for problems such as cross-site scripting, SQL injection, command injection, path traversal and insecure server configuration. Because DAST works on the deployed system, it sees what really answers on the network: headers, TLS settings, exposed paths, error handling and the behaviour of the whole stack.

The trade-offs are the mirror image of SAST. DAST needs a running, reachable environment, so it comes later in the lifecycle. It cannot tell you which line of code to change, only which request misbehaved. Coverage depends on how well the scanner can crawl the application, log in and understand your API, so poorly configured scans can miss large parts of it. Like SAST, it struggles with business logic.

Where SCA and IAST fit

Modern applications consist mostly of open-source dependencies, which is why SCA matters even if your own code is clean. It flags known vulnerable components and, in some tools, whether the vulnerable function is actually reachable from your code. Semgrep's documentation, for example, describes reachability analysis for supply chain scans.

IAST sits between the two approaches. Because it sees both the request and the code path, it can give precise, low-noise results, but it only covers what your tests exercise, it requires an agent for your language and runtime, and it adds some operational overhead. Treat it as an optional refinement once SAST, SCA and DAST are in place.

Fitting them into the lifecycle and CI/CD

A practical pattern is to match each technique to the earliest stage where it works. NIST's Secure Software Development Framework (SP 800-218, version 1.1) is deliberately outcome-based and does not prescribe tools, but it expects organisations to verify code and test executable code for vulnerabilities. NIST has also published a draft revision, SSDF version 1.2, as an initial public draft in December 2025; its comment period has closed, so check the final text before citing it in a contract.

OWASP SAMM version 2.0 treats security testing as one of three practices in its Verification function. It describes a scalable baseline of automated testing next to a deeper stream of manual testing and penetration tests, which is a useful way to explain why you need both.

• In the IDE and on pull requests: SAST, secret detection and SCA with fast, narrow rule sets
• On every build: full SAST and SCA with a quality gate that blocks only high-confidence, high-severity findings
• On a staging environment: DAST baseline scans after each deployment, deeper authenticated scans nightly or weekly
• Before major releases and after big changes: manual testing of high-risk components

Managing false positives

A scanner nobody trusts gets switched off. Start with a small, well-tuned rule set, tune it against your own code, and widen it later. Block the build only on findings you have confirmed as real classes of risk, and report everything else as a backlog. Record suppressions with a reason and an expiry date so they do not become permanent blind spots.

Assign an owner for triage, not just for scanning. Without someone who decides what is a true positive, the output turns into noise within weeks.

Choosing tools and knowing when you need people

There is no single best product, and OWASP states that it does not endorse any listed scanner. Examples help you compare categories. Among DAST tools, ZAP is free and open source under the Apache 2.0 licence; since September 2024 it has been developed as ZAP by Checkmarx, and the project says it stays open source and under its core team's control. Burp Suite from PortSwigger has a free community edition, a professional edition for hands-on testers and an enterprise-oriented DAST edition. For SAST, SonarQube Server is a self-managed tool covering many languages and infrastructure as code, and Semgrep combines code scanning, dependency scanning and secrets detection on one platform. Snyk and Checkmarx One bundle several scan types, including SAST and SCA, into commercial platforms.

Compare tools on your own stack: supported languages and frameworks, API and single-page-app support for DAST, CI integration, how findings are triaged, where data is processed, and total cost including the people who run it.

• Open-source tools are a good start if you have staff time to tune and maintain them
• Commercial platforms reduce integration work and offer reporting, at a licence cost
• A managed application security testing service makes sense when you lack the people to triage findings, need coverage across many applications, or must show regular evidence to auditors or customers
• A manual penetration test is needed when logic flaws, access control or a high-impact release are at stake; scanners complement it but cannot replace it