SAST vs DAST vs IAST vs SCA: Which Security Testing Do You Need?
Application security testing comes with a lot of acronyms. Each method looks at your application from a different angle, and no single one catches everything. Here is how they compare.
The four approaches
- SAST (Static Application Security Testing) analyses source code without running it.
- DAST (Dynamic Application Security Testing) tests the running application from outside.
- IAST (Interactive Application Security Testing) instruments the running application from inside, observing code execution during tests.
- SCA (Software Composition Analysis) identifies open-source dependencies and their known vulnerabilities.
Comparison
| SAST | DAST | IAST | SCA | |
|---|---|---|---|---|
| Needs source code | Yes | No | Agent in app | Manifests or binaries |
| Needs running app | No | Yes | Yes | No |
| When it runs | Early, on commit | After deploy | During testing | On commit and continuously |
| Finds injection | Yes | Yes | Yes | Only in dependencies |
| Finds access control flaws | Rarely | With multi-user testing | Limited | No |
| Finds config issues | Some in code | Yes | Some | No |
| Finds vulnerable libraries | No | Sometimes | Yes | Yes |
| False positives | Higher | Lower | Low | Low to medium |
| Pinpoints code location | Yes | No | Yes | Yes, the package |
Strengths and blind spots
SAST catches issues early and points to exact lines, but struggles with context and produces noise.
DAST sees real behaviour, including deployment configuration, and its findings are concrete, but it only tests what it can reach and does not point to code.
IAST combines runtime evidence with code location, but requires instrumenting your app and depends on test coverage to exercise code paths.
SCA is essential because most application code is open-source dependencies. It is fast and accurate for known CVEs, though many reported vulnerabilities are not reachable in your usage.
What none of them reliably catch
Business logic flaws and authorisation bugs, such as IDOR and cross-tenant access, need testing that understands users, roles and intent. Traditional tools of every type struggle here. Penetration testing, human or AI-driven, fills this gap.
A practical stack for small teams
- SCA from day one, with dependency alerts in your code host.
- Secret scanning with push protection.
- SAST with a small, high-confidence rule set on pull requests.
- AI-driven dynamic testing of the running app and APIs, with multiple identities, on each release.
- Periodic deeper testing of high-risk workflows as you grow.
IAST makes sense later, if you have strong automated test suites and want to combine runtime and code insight.
How SecurityInfinity fits
SecurityInfinity combines static analysis for secrets and insecure code with dynamic AI pentesting agents for web, API and network, so findings from code are confirmed against the running application, and every result comes with a fix. Start free.
Frequently asked questions
Which should I start with?
SCA and secret scanning are the cheapest and fastest wins. Add dynamic testing next, because it finds exploitable issues in what you actually deployed.
Is IAST better than DAST?
It gives richer detail but needs instrumentation and good test coverage. DAST is easier to adopt and tests real external behaviour.
Does SCA replace patch management?
No. SCA tells you what is vulnerable; patch management is the process of updating it.