SAST vs. DAST

SAST and DAST are two types of application security testing used to detect security vulnerabilities. In the realm of software development, ensuring the security of applications is paramount. This is where tools like Static Application Security Testing (SAST) and Dynamic Application Security Testing (DAST) come into play, each serving a unique purpose in identifying vulnerabilities that could compromise application security.

The synergy between SAST and DAST equips development teams with a comprehensive security testing strategy. While SAST allows for early detection of vulnerabilities in code, DAST offers a practical assessment of how an application behaves under attack once it’s live.

What is SAST?

SAST dives deep into the source code without executing it, offering a white-box testing approach. It’s like having an expert reviewer pore over your code, pinpointing areas prone to security breaches such as SQL injections or buffer overflows. By integrating SAST early in the development lifecycle, ideally right after code is committed, developers receive immediate feedback on potential security issues, allowing for swift corrections.

This proactive stance on security ensures that vulnerabilities are addressed long before the code reaches deployment, saving time and resources while fostering a culture of security mindfulness among developers.

What is DAST?

DAST, on the other hand, takes an outsider's perspective, performing black-box testing on running web applications to uncover vulnerabilities an attacker could exploit. It simulates cyber attacks on the application, scanning for issues like cross-site scripting or broken authentication flaws.

DAST provides a hacker's eye view of the application, highlighting security weaknesses in the deployed environment and offering insights on how to fortify defenses against real-world attacks.

Employing both tools in tandem ensures a robust security posture, catching different types of vulnerabilities at various stages of the development lifecycle. For teams committed to shipping secure software, balancing SAST’s early intervention with DAST’s real-world testing provides a holistic approach to application security.

SAST is an important way to catch security vulnerabilities early on while the code is still being developed, and long before it’s been deployed. Catching vulnerabilities earlier in the development process typically makes them cheaper and easier to fix. This early detection mechanism not only mitigates the risk of potential security breaches but also aligns with best practices for developing secure applications in today’s fast-paced software development environments.

By prioritizing security from the beginning, teams can significantly reduce the likelihood of costly and damaging security incidents post-deployment, reinforcing the trust users place in the application and the organization behind it. In this way, SAST not only safeguards the application but also upholds the reputation and reliability of the development team, marking a commitment to excellence and trustworthiness in software development.

DAST helps you catch security issues and vulnerabilities in your applications that are unlikely to be caught by other traditional testing methods that focus on the code and technology within your application. DAST simulates attacks on the application to identify security weaknesses where an attacker could get in, so you can fix them before they can be exploited by real attackers.

Additionally, the ability of DAST to test applications in their running state offers unique insights into runtime behaviors and environment-specific vulnerabilities, which static analysis might overlook. This includes testing for misconfigurations, authentication and session management flaws, and operational issues that only manifest when the application is live.

SAST and DAST are becoming increasingly common tools for DevOps teams.

According to GitLab’s 2022 Global DevSecOps Survey, 53% of developers now run SAST scans (up from less than 40% in 2021) and 55% of developers run DAST scans (up from 44% in 2021).

SAST and DAST largely detect different types of vulnerabilities and security issues. Here are some of the security issues SAST and DAST can identify.

SAST can detect:

• SQL injection
• Buffer overflows
• XML External Entity (XXE) vulnerabilities
• Critical security vulnerabilities identified in industry standards like OWASP Top 10 and SANS/CWE Top 25

DAST can detect:

• Cross-site scripting (XXS)
• SQL injection
• Broken authentication flaws
• Encryption issues
• Misconfigurations of your application server or databases
• Incorrect assumptions about security controls that may not be visible from the source code

To get the full benefits of SAST and DAST, it’s best to:

• Build/Integrate SAST and DAST into your team’s workflow and CI/CD pipeline.
• Make SAST and DAST auto-run so your team doesn’t have to manually initiate the tests.
• Ensure running SAST and DAST can’t be bypassed or forgotten.
• Put restrictions in place so that code with detected vulnerabilities cannot be merged without the proper approvals.
• Make sure the SAST and DAST analyzers you use are updated regularly so you benefit from the latest vulnerabilities definitions.
• Use SAST and DAST in a way that all of your teams — development, ops and security — can easily see the results of scans and collaborate to fix security issues.

You’ll want to use both SAST and DAST to help your team ship secure software and catch security issues earlier when they’re less likely to slow you down.

SAST should be run very early in the software development lifecycle, ideally as soon as code is committed. This means that security vulnerabilities in the code can be detected and highlighted to the person who committed the code while it’s still fresh in their mind.

DAST should be run anytime you make a change to your application, ideally when it’s deployed in a test environment so you can catch issues before they make it to production. DAST can also be used to continuously monitor live web applications for issues like cross-site scripting or broken authentication flaws.

What they scan

SAST scans source code, while DAST scans applications and APIs or web services your application connects to, such as GraphQL, REST, and SOAP.

When they scan

SAST happens early in the software development lifecycle shortly after code is written, while DAST happens later in the development lifecycle once there’s a working application running in a test environment, or even on production code.

Difference in the types of testing

SAST is white-box testing that looks for vulnerabilities inside the application and code, while DAST is black-box testing that looks for vulnerabilities that could allow an outside attacker to get in.

Having access to course code

SAST tools scan the source code of an application, while DAST tools do not have access to source code.

Difference in language dependence

Because SAST is scanning your source code, it’s specific to the programming languages and development frameworks used, and the SAST tool you use needs to support the programming language you are using — whether it’s C++, Python, Go, React, Ruby, or something else.

Unlike SAST, DAST doesn’t care what languages or frameworks your application is built on because it’s testing your application from the outside like an attacker would.

False positives

SAST tends to produce more false positives than DAST. This is because it’s focused on source code and doesn’t have all the context to know if one line of code that looks problematic is actually solved somewhere else. Some DAST providers, such as GitLab, are able to identify some false positives in SAST.

GitLab’s DevSecOps platform can help you get the most out of SAST and DAST — and much more — to help you improve the security of your applications without sacrificing speed.

Learn more:

• Our documentation
• Our solutions page on DevSecOps, security, and governance