Static Application Security Testing (SAST) and Dynamic Application Security Testing (DAST) are complementary approaches to application security. Understanding when and how to use each is critical for building a comprehensive security testing strategy.
What is SAST?
Static Application Security Testing (SAST) analyzes source code, bytecode, or binaries without executing the application. It's a "white-box" testing approach that examines the code from the inside out.
Key Characteristics of SAST:
- Early Detection: Finds vulnerabilities during development, before code is deployed
- Code Coverage: Analyzes 100% of code paths, including rarely executed branches
- Pinpoint Location: Identifies exact file, line number, and code snippet with the vulnerability
- Fast Feedback: Integrates into CI/CD pipelines, providing results in minutes
- No Runtime Required: Doesn't need a running application or test environment
Common Vulnerabilities Found by SAST:
- SQL Injection (parameterized query violations)
- Cross-Site Scripting (XSS) from unescaped output
- Hardcoded credentials and API keys
- Insecure cryptographic implementations
- Path traversal vulnerabilities
- Command injection flaws
- Insecure deserialization
- Race conditions and concurrency issues
SAST Limitations:
- False Positives: Can flag code as vulnerable when it's actually safe (e.g., sanitized input)
- Configuration Blind Spots: Doesn't detect misconfigurations in web servers, databases, or infrastructure
- Runtime Context Missing: Can't identify authentication bypass, business logic flaws, or session management issues
- Third-Party Dependencies: Limited visibility into compiled libraries (though SCA tools help here)
What is DAST?
Dynamic Application Security Testing (DAST) tests a running application by simulating real-world attacks. It's a "black-box" approach that examines the application from an attacker's perspective.
Key Characteristics of DAST:
- Real-World Testing: Simulates actual attack scenarios against a running application
- Runtime Vulnerabilities: Detects issues only visible when the app is running
- Configuration Testing: Finds misconfigurations in servers, APIs, and databases
- Technology Agnostic: Works with any web application regardless of programming language
- Proof of Exploitability: Confirms vulnerabilities are actually exploitable, reducing false positives
Common Vulnerabilities Found by DAST:
- Authentication and session management flaws
- Missing security headers (CSP, HSTS, X-Frame-Options)
- SSL/TLS misconfigurations
- Server misconfigurations (directory listing, verbose errors)
- CORS policy violations
- Business logic vulnerabilities
- API rate limiting issues
- Clickjacking vulnerabilities
DAST Limitations:
- Late in Lifecycle: Requires a deployed, running application—can't test during early development
- Code Path Coverage: Only tests reachable code paths; can miss dormant vulnerabilities
- No Source Context: Doesn't show exact code location—developers must trace back to the source
- Slower Execution: Takes hours to complete comprehensive scans
- Test Data Dependency: Requires realistic test data and proper application state
SAST vs DAST: Side-by-Side Comparison
| Criteria | SAST | DAST |
|---|---|---|
| Testing Approach | White-box (inside-out) | Black-box (outside-in) |
| When to Run | During development, on every commit | In staging/pre-production |
| Speed | Fast (minutes) | Slow (hours) |
| Coverage | 100% code paths | Only executed paths |
| False Positives | Higher (needs triage) | Lower (exploitability proven) |
| Remediation Guidance | Precise (file + line number) | General (URL + vulnerability type) |
| Best For | Injection flaws, hardcoded secrets | Auth issues, config errors |
When to Use SAST
SAST is Ideal For:
- ✓ Shift-Left Security: Finding vulnerabilities early when they're cheapest to fix
- ✓ Developer Feedback: Providing immediate, actionable guidance during coding
- ✓ Pre-Commit Checks: Blocking commits with critical vulnerabilities (secrets, SQL injection)
- ✓ Compliance Requirements: Satisfying regulatory mandates for code analysis (PCI-DSS, SOC 2)
- ✓ Legacy Code Audits: Scanning large codebases for latent vulnerabilities
When to Use DAST
DAST is Ideal For:
- ✓ Pre-Production Validation: Final security check before releasing to production
- ✓ Runtime Configuration Testing: Validating security headers, SSL/TLS, server hardening
- ✓ Third-Party Integrations: Testing APIs and services you don't control
- ✓ Penetration Testing Prep: Identifying low-hanging fruit before hiring external pentesters
- ✓ Continuous Monitoring: Regular scans of production to catch configuration drift
The Optimal Strategy: Use Both
The most effective security testing strategy combines SAST and DAST at different stages of the SDLC:
Recommended CI/CD Pipeline
Developer Workstation
IDE plugin (SAST) - Real-time feedback while coding
Pre-Commit Hook
Secrets scanning (SAST) - Block hardcoded credentials
Pull Request Build
Full SAST scan + SCA - Fail on critical/high findings
Staging Deployment
DAST scan - Test running application for runtime issues
Pre-Production Gate
Review DAST results, approve for production
Production
Monthly DAST scans - Detect configuration drift
Popular Tools
SAST Tools
- SonarQube: Open-source, supports 27+ languages
- Semgrep: Lightweight, fast, customizable rules
- Snyk Code: Developer-friendly, IDE integration
- Checkmarx: Enterprise-grade, deep analysis
- GitHub CodeQL: Built into GitHub, query-based
DAST Tools
- OWASP ZAP: Free, open-source, community-driven
- Burp Suite: Industry standard, powerful scanner
- Acunetix: Fast, automated web vulnerability scanner
- Netsparker: Low false positives, proof-based scanning
- StackHawk: API-focused, CI/CD native
Ready to Implement Comprehensive Security Testing?
Securus Mind integrates both SAST and DAST into a unified platform with intelligent triage and remediation workflows.