DAST vs SAST: Understanding the Key Differences in Application Security Testing

Application Security Testing (AST) is the process of identifying security vulnerabilities in software applications. As applications become more complex and attack surfaces grow, AST has become essential for organizations of all sizes. Two primary approaches dominate the AST landscape: Static Application Security Testing (SAST) and Dynamic Application Security Testing (DAST). Understanding the differences between these methodologies is crucial for building a comprehensive security strategy.

SAST, also known as "white-box testing," analyzes an application's source code, bytecode, or binaries without executing the program. It examines the code structure to identify potential security vulnerabilities. How SAST Works: • Scans source code, bytecode, or compiled binaries • Analyzes code paths and data flows • Identifies vulnerabilities before the application runs • Provides line-by-line insights into security issues Common Vulnerabilities Detected by SAST: • SQL Injection patterns • Cross-Site Scripting (XSS) vectors • Buffer overflows • Hardcoded credentials • Insecure cryptographic implementations • Code quality issues that could lead to vulnerabilities

Early Detection SAST can identify vulnerabilities early in the development lifecycle, when they're cheapest to fix. Developers can address issues before code is even committed. Complete Code Coverage SAST tools can analyze 100% of the codebase, including code paths that might rarely execute in production. Precise Location SAST provides exact line numbers and code snippets where vulnerabilities exist, making remediation straightforward. Language-Specific Analysis Modern SAST tools understand programming language semantics, enabling more accurate detection. Integration with IDEs Many SAST tools integrate directly with development environments, providing real-time feedback.

False Positives SAST tools often report potential issues that aren't actually exploitable, requiring manual review. No Runtime Context SAST cannot detect vulnerabilities that only manifest at runtime, such as configuration issues or environment-specific problems. Limited Third-Party Visibility SAST may miss vulnerabilities in compiled third-party libraries or dependencies. Language Dependency Each programming language requires specific SAST tooling and rules.

DAST, also known as "black-box testing," tests applications in their running state. It simulates external attacks by interacting with the application through its interfaces, just like an attacker would. How DAST Works: • Tests the application while it's running • Sends malicious inputs to application endpoints • Analyzes responses for security weaknesses • Requires no access to source code Common Vulnerabilities Detected by DAST: • Authentication and session management flaws • Server misconfigurations • Runtime injection vulnerabilities • Cross-Site Request Forgery (CSRF) • Security header issues • API vulnerabilities

Real-World Testing DAST tests the actual running application, including the server environment, configurations, and third-party integrations. Technology Agnostic DAST doesn't care what language or framework your application uses — it tests the exposed interfaces. Fewer False Positives Because DAST tests real exploitation scenarios, confirmed vulnerabilities are typically exploitable. Environment Awareness DAST can identify configuration issues and environment-specific vulnerabilities. No Source Code Required Useful for testing third-party applications or legacy systems where source code isn't available.

Late Detection DAST requires a running application, meaning vulnerabilities are found later in the development cycle. Limited Code Coverage DAST can only test code paths that are reachable through application interfaces. Cannot Pinpoint Source DAST identifies that a vulnerability exists but may not indicate exactly where in the code. Requires Running Environment Setting up and maintaining test environments adds overhead.

Testing Approach: • SAST: Inside-out (white-box) • DAST: Outside-in (black-box) When Testing Occurs: • SAST: During development, before deployment • DAST: After deployment, in running environment Code Access Required: • SAST: Yes (source code or binaries) • DAST: No (tests through interfaces) Vulnerability Location: • SAST: Exact line in source code • DAST: Endpoint/page level False Positive Rate: • SAST: Higher • DAST: Lower Coverage: • SAST: All code paths • DAST: Only reachable paths

Neither SAST nor DAST alone provides complete security coverage. The most effective strategy combines both approaches: Shift Left with SAST Integrate SAST into your CI/CD pipeline to catch vulnerabilities early. Run SAST on every commit to prevent new vulnerabilities from entering the codebase. Validate with DAST Use DAST to test your staging and production environments. DAST catches configuration issues and validates that SAST-identified vulnerabilities have been properly remediated. Add IAST for Complete Coverage Interactive Application Security Testing (IAST) combines SAST and DAST approaches, analyzing applications from within during runtime. How TEPTEZ Helps TEPTEZ provides integrated DAST and SAST capabilities in a single platform. Our solution: • Correlates findings between SAST and DAST • Reduces false positives through cross-validation • Prioritizes vulnerabilities based on exploitability • Provides unified reporting and remediation guidance