SAST and DAST: Application Security Testing | Decripte

SAST (Static Application Security Testing) and DAST (Dynamic Application Security Testing) represent two fundamental and complementary methodologies in the field of application security, each with distinct but equally important approaches to identifying vulnerabilities. SAST operates through static analysis of source code, bytecode or binaries without running the application, examining the code for patterns that indicate potential vulnerabilities such as SQL injection, XSS, buffer overflows and business logic flaws. This "white-box" approach makes it possible to identify problems early in the development cycle (shift-left security), providing developers with precise feedback on the exact location of the vulnerable code. On the other hand, DAST simulates real attacks against the running application, testing it in a "black-box" manner as an external attacker would, without access to the source code. This technique reveals vulnerabilities that only manifest at runtime, such as configuration flaws, authentication and authorization issues, and vulnerabilities that arise from the interaction between different components. When implemented together in an integrated DevSecOps strategy, SAST and DAST cover each other's blind spots, creating a defense in depth that detects both vulnerabilities introduced during development and those that emerge during application execution in real environments.

SAST: Static Analysis

SAST examines source code, bytecode or binaries without running the application, identifying vulnerabilities during development.

SAST Advantages

• Early detection: Finds bugs before deployment
• Code coverage: Analyzes 100% of the code, including paths that are not executed
• Root cause: Shows the exact line of vulnerable code
• No runtime needed: Does not require the application to be running
• CI/CD integration: Automation in the build pipeline

SAST Limitations

• High false positives - requires tuning
• Does not detect configuration vulnerabilities
• Does not test business logic at runtime
• Language-specific - each language needs its own scanner

SAST Tools

DAST: Dynamic Analysis

DAST tests the running application, simulating real attacks through black-box testing, without access to the source code.

DAST Advantages

• Runtime testing: Tests the application like a real attacker
• Configuration issues: Detects configuration flaws
• Low false positives: Confirmed exploitable vulnerabilities
• Language-agnostic: Works for any stack
• Production-like: Tests in an environment similar to production

DAST Limitations

• Late detection - vulnerabilities found after the code is finished
• Limited code coverage - only tests accessible flows
• No code details - does not show the vulnerable line
• Requires the application to be deployed and running

DAST Tools

SAST + DAST: Combined Strategy

Using SAST and DAST together covers the blind spots of each approach, creating a robust AppSec program.

      # CI/CD pipeline with SAST + DAST
      stages:
      - build
      - sast
      - test
      - dast
      - deploy
      sast_scan:
      stage: sast
      script:
      - semgrep --config=auto --json -o sast-results.json
      - sonar-scanner
      artifacts:
      reports:
      sast: sast-results.json
      dast_scan:
      stage: dast
      script:
      - docker run -t owasp/zap2docker-stable zap-baseline.py
      -t https://staging.app.com -r dast-report.html
      artifacts:
      reports:
      dast: dast-report.html
      

IAST: Interactive Application Security Testing

IAST combines SAST and DAST, instrumenting the application to monitor it at runtime, obtaining the code coverage of SAST with the runtime accuracy of DAST.

• Contrast Security: IAST leader, embedded agents
• Seeker (Synopsys): Runtime analysis with code insight
• Hdiv Security: Runtime application self-protection

DevSecOps Integration

• SAST in pre-commit hooks and pull requests
• DAST in staging environments before production
• Quality gates: block builds with critical vulnerabilities
• Developer feedback loops: integrate with IDEs (SonarLint)
• Vulnerability management: centralize findings on a single platform