Introduction#
Static Application Security Testing (SAST) and Dynamic Application Security Testing (DAST) are complementary methods for finding software vulnerabilities. SAST analyzes code at rest, while DAST probes running applications. Choosing the right mix improves detection coverage and reduces costly fixes later in the lifecycle.
What SAST does (static, early-stage)#
SAST inspects source code, bytecode, or compiled binaries without executing the application. It’s a “white-box” approach that detects issues like:
- SQL injection patterns in code paths
- Unsafe deserialization and insecure API usage
- Hardcoded secrets and insecure cryptography usage
Where to run SAST:
- In the developer IDE for immediate feedback
- As part of pre-merge CI checks
- During nightly builds for slow, deep scans
Benefits:
- Finds vulnerabilities early (cheaper to fix)
- Integrates into developer workflows Limitations:
- False positives for unreachable code
- Can’t detect runtime configuration issues or authentication flaws
What DAST does (dynamic, runtime)#
DAST treats the application as a black box and tests the running system from the outside. It simulates attacker behavior and looks for:
- Cross-site scripting (XSS)
- Auth/session logic flaws
- Server misconfiguration and injection points visible at runtime
Where to run DAST:
- Against staging or pre-production environments
- During QA test runs and periodic security scans
Benefits:
- Finds runtime and environment-dependent vulnerabilities
- Validates end-to-end behavior (authentication, input validation) Limitations:
- Requires a deployed app and testable interfaces
- May miss issues hidden in source code or internal libraries
Practical workflow: use both, in sequence#
A practical pipeline combines SAST and DAST:
- Developer stage — SAST in IDE and pre-commit hooks
- CI pipeline — fast SAST checks on pull requests
- Nightly/merge builds — deep SAST scan + dependency scanning (SCA)
- Staging environment — DAST scans and authenticated tests
- Production monitoring — runtime application self-tests and WAF telemetry
Example snippets:
# Simple DAST-style check (curl)
curl -s -I https://staging.example.com/login | head -n 5
# Run a SAST tool (example)
semgrep --config auto src/How to prioritize results#
- Triage by exploitability (public input, auth bypass)
- Fix code with SAST findings first when they prevent exploits
- Use DAST findings to harden runtime (rate limits, WAF rules, config)
Conclusion#
SAST and DAST are not alternatives — they’re partners. SAST catches code-level defects early; DAST validates real-world exposure at runtime. Implement both in stages: shift-left with SAST, validate with DAST, and continuously monitor in production. Start by adding lightweight SAST checks to PRs and schedule regular DAST scans against staging environments.
Co-authored by Vishwakarma, Deeps 2nd Brain
