SAST vs. DAST

Modern applications are under constant attack. From zero-day exploits to misconfigurations in production, every layer of an application stack can expose security gaps. Yet, too often, security testing is treated as a last step if it happens at all. To build resilient software, SAST and DAST must be embedded from development through deployment.

These complementary approaches enable teams to catch code flaws early and uncover runtime risks before attackers can. Used together, they transform security testing from a reactive effort into a continuous, proactive discipline. This guide explains how SAST and DAST fit into today’s secure development pipelines and why relying on just one leaves critical blind spots.

TL; DR:

SAST finds flaws in code before deployment, while DAST spots vulnerabilities in live apps. Together, they cover both sides of security and strengthen DevSecOps.

Static Application Security Testing (SAST) is a white-box testing method that analyzes an application's source code, bytecode, or binaries for security vulnerabilities, without executing the program. It provides complete visibility into code structure, enabling early detection of flaws such as SQL injection, buffer overflows, and hardcoded secrets during development.

SAST uses automated scanning, pattern matching, and control and data flow analysis to identify insecure coding practices and trace how data moves through the application. It also supports analysis of compiled binaries when source code is unavailable. Common use cases include meeting compliance standards like PCI DSS, protecting sensitive data in financial applications, and enabling DevSecOps teams to embed security checks into CI/CD pipelines.

Types of Vulnerabilities SAST Detects

• SQL Injection: SAST detects unsafe code where user input is directly used in SQL queries. This prevents attackers from manipulating database commands to access or alter data.

• Cross-Site Scripting (XSS): SAST identifies spots where user input is improperly handled and rendered in web pages. This helps block attackers from injecting malicious scripts into users' browsers.

• Buffer Overflows: SAST flags code where data exceeds memory limits, potentially leading to crashes or code execution. These flaws are common in low-level languages like C or C++.

• Hard-Coded Secrets: SAST scans for credentials, API keys, or tokens embedded directly in the code. Exposing these secrets can lead to unauthorised access or data breaches.

• Insecure Function Use: SAST detects the use of outdated or unsafe functions known to cause vulnerabilities. This helps developers replace risky code with safer alternatives.

Strengths & Limitations of SAST

Dynamic Application Security Testing (DAST) is a black-box testing method that analyzes running applications from an external perspective to identify vulnerabilities without accessing internal source code. This "outside-in" approach simulates attacker behavior to uncover real-time security flaws across any programming language or platform.

DAST tools begin by crawling applications to map available endpoints, then simulate attack techniques such as SQL injection, cross-site scripting (XSS), and authentication exploits. They analyze the application's responses for abnormal behavior and generate detailed reports with severity ratings and remediation guidance, helping security teams prioritize fixes effectively.

This testing approach is commonly used to validate security in pre-production environments, support penetration testing for compliance standards such as PCI DSS, and enable continuous monitoring of live applications to detect newly introduced vulnerabilities.

Types of Vulnerabilities DAST Detects

• Server Configuration Issues: DAST can detect insecure server setups, such as exposed directories, outdated software versions, and improper SSL configurations. These misconfigurations can provide attackers with unintended access or sensitive system information.

• Authentication and Session Management Flaws: It identifies weaknesses like weak password policies, session fixation, or improper logout mechanisms. Such flaws can allow attackers to hijack user sessions or bypass authentication altogether.

• Input Validation Problems: DAST tests for vulnerabilities like SQL injection and cross-site scripting (XSS) that occur when user input is not properly sanitized. These issues can let attackers inject malicious code or commands into the application.

• Runtime-Specific Vulnerabilities: It uncovers security issues that only appear while the application is running, such as memory leaks, logic flaws, or time-of-check/time-of-use (TOCTOU) bugs. These can be difficult to detect through static analysis alone.

• Network-Level Security Issues: DAST tools can identify problems like unsecured data transmission, open ports, and weak encryption. These vulnerabilities can expose sensitive data to interception or unauthorised access during communication.

Strengths & Limitations of DAST

Both SAST and DAST are useful, but they serve different needs.

When to Use SAST

• Early Detection: Use SAST during the coding phase to catch security flaws before the application is compiled or deployed, reducing costly fixes later.

• Source Access: SAST is ideal when you have full access to the application’s source code, allowing a detailed examination of logic and data flow for vulnerabilities.

• Coding Standards: Use SAST to automatically check if developers follow secure coding best practices and guidelines consistently throughout the codebase.

• Compliance Support: Many regulatory standards require static code analysis as part of the security assessment process to ensure secure development practices.

• Pipeline Integration: SAST tools can be automated to run on every code commit, providing continuous feedback to developers and preventing vulnerable code from progressing further.

When to Use DAST

• Runtime Testing: Use DAST when the application is deployed or in a test environment to identify security flaws visible only during runtime.

• Source Independence: DAST is ideal when you don’t have access to the source code but need to test the application’s external behavior and exposed interfaces.

• Control Validation: Use DAST to verify that authentication, session management, and input validation mechanisms work correctly under attack scenarios.

• Environment Detection: DAST helps uncover misconfigurations, server vulnerabilities, and deployment-related security gaps that static analysis can miss.

• Compliance Testing: DAST is commonly used in penetration testing to simulate real-world attacks and meet compliance requirements for dynamic security assessments.

SAST and DAST are not competitors, they are allies. While SAST covers the internal workings of the code, DAST focuses on what an external attacker would see. Together, they provide comprehensive coverage. This combined approach is often referred to as "hybrid testing" or "shift-left and shift-right security."

1. Complementary Detection: SAST and DAST detect different types of vulnerabilities. SAST excels at finding code-level issues, while DAST identifies runtime flaws. Together, they cover a broader range of threats, including injections, XSS, IDOR, and misconfigurations. This dual coverage reduces blind spots in your security posture.

2. Early and Late-Stage Protection: SAST protects the application during development, catching flaws before they are compiled or deployed. DAST protects in later stages by simulating real-world attacks on a live app. Using both ensures security is maintained throughout the entire SDLC.

3. Cost-Effectiveness: Fixing issues found by SAST early in the coding phase is cheaper and faster than addressing them post-deployment. DAST validates that those fixes are effective in the real world. This layered approach reduces long-term security costs and breach risks.

4. CI/CD Integration and DevSecOps Alignment: SAST fits well in CI/CD pipelines for real-time feedback, while DAST can be added in staging to test final builds. Together, they support secure DevOps practices by enforcing security gates at multiple points. This ensures continuous, automated, and proactive security.

5. Improved Compliance and Risk Management: Many industry regulations (like PCI DSS, HIPAA, and ISO 27001) recommend or require both static and dynamic testing. Combining SAST and DAST helps meet these requirements and provides a well-documented security testing strategy. This reduces legal risk and builds trust with stakeholders.

1. Embedding SAST in Development

SAST integrates directly into the development phase, scanning source code within IDEs and CI pipelines. By running automated checks on every commit, it identifies vulnerabilities such as hardcoded secrets, insecure logic, and input flaws early, before they progress downstream.

2. Securing Build Pipelines

During automated builds, SAST ensures that only secure code moves forward. Integration with CI tools like Jenkins or GitLab CI enables security gates, preventing vulnerable builds from being promoted. This shift-left approach reduces remediation costs and improves overall code quality.

3. Deploying DAST in Staging

DAST enters later in the pipeline, scanning fully deployed applications in staging environments. It simulates external attacks to uncover runtime vulnerabilities, configuration issues, and security flaws in exposed interfaces, offering a realistic view of potential risks before production release.

4. Continuous Monitoring in Production

In production, DAST provides ongoing validation by scanning live applications without disrupting normal operations. It detects newly introduced vulnerabilities caused by code changes, configuration drift, or emerging threat patterns, helping teams maintain a secure operational posture.

5. Achieving Full Coverage

Combining SAST and DAST within the DevSecOps pipeline delivers comprehensive security coverage. SAST protects the codebase from the inside out, while DAST validates the deployed application from the outside in. Together, they enable continuous, automated security testing across the entire software lifecycle.

SAST and DAST address different layers of application security. SAST uncovers code-level flaws early, while DAST identifies runtime vulnerabilities in live environments. The real value lies in using both strategically.

Mature programs integrate SAST into development and DAST into staging and production, embedding continuous security testing into workflows and team practices. Done right, this strengthens resilience, fosters trust, and gives your applications a clear edge in today’s threat landscape.