SAST vs DAST: Understanding the Key Differences

Organizations face a continuous threat against their confidential data and software applications with rising cyber incidents. Hence, security testing has become vital to produce secure applications to defend against these threats.

SAST and DAST are two reliable methods in the realm of security testing. These methods help to test applications in different ways to identify vulnerabilities. SAST analyzes the source code and DAST tests applications in the running state.

But which one of these methods is more suitable for your security testing needs? Let’s find in this article through the SAST vs DAST comparison. Keep reading for complete information and to understand the differences between SAST and DAST.

Understanding DAST and SAST Security Testing Methods

DAST and SAST automate application security testing and help discover potential vulnerabilities that can compromise security. Imagine SAST (Static Application Security Testing) as an architect. An architect has a blueprint to check for vulnerable spaces even before the building is created.

Similarly, SAST tools can identify vulnerabilities by scanning application source code. It does not require an application to be built in advance. SAST is a kind of white box testing technique that tests applications from the inside by examining the code. Whitebox testing refers to a security testing technique in which the test expert is aware of the inner workings of an application.

DAST (Dynamic Application Security Testing) is like a vigilant guard who tries to break into a building by identifying weak spots. In this case, the building exists physically, and the guard inspects it from outside. Hence, DAST is a security testing method that involves testing applications from outside, which is the blockbox testing technique.

In DAST, simulated attacks are performed on the target application with a set of invalid and valid inputs to examine its behavior like a hacker. DAST tests applications in the running state, unlike SAST, which tests static code. Hence, developing applications is a prerequisite for DAST.

Today SAST and DAST have become an integral part of modern development processes to produce secure software applications. According to the survey report by Gitlab, 55% of developers run DAST scans, and 53% run SAST scans.

SAST vs DAST: What are the Key Differences?

DAST and SAST have become crucial methods for software development teams to ensure robust security for applications. They are two different approaches with various benefits and limitations. Let’s see a full comparison of DAST vs SAST to understand the variance better.

Vulnerabilities Detected

Static Application Security Testing (SAST) can help to identify vulnerabilities at the code level including Cross-site Scripting (XSS), SQLi, and buffer overflows. The key advantage of this testing technique is to uncover insecure coding practices that lead to vulnerabilities.

DAST can also detect these kinds of vulnerabilities. In fact, it can identify common vulnerabilities like OWASP Top 10. It can detect these security weaknesses with simulated attacks. However, it is more efficient at detecting runtime vulnerabilities like server configuration issues.

Implementation Stage

Traditionally, security testing was an afterthought that was performed at the end of the SDLC. However, modern development methods embrace security testing as an integral part of the SDLC. Therefore, security has been shifted to today’s SDLC.

SAST is leveraged at the initial stage of an SDLC to evaluate the source code and identify security flaws. Often, SAST tools are integrated into coding tools like IDEs to discover security vulnerabilities even before the code is compiled.

DAST helps to test applications in the running state. Hence, it is implemented when the code is compiled, and the application is ready for execution. It performs simulated attacks on the application to analyze the behavior and detect weak spots.

Techniques of Testing

Since SAST is a white box testing technique, it analyzes applications from the inside. This means that it scans the source code of an application to discover potential vulnerabilities. SAST looks for common security loopholes and errors that could result in compromised security.

In contrast, DAST examines applications from outside using the front end as it follows the backbox technique of security testing. It performs automated simulated attacks on an application by sending inputs (invalid and valid) and observing application behavior.

DAST identifies security flaws in real-world scenarios when an application is running in its environment. However, SAST only identifies code-level security flaws that may be wrong. Hence, the former has an advantage here when it comes to the SAST vs DAST battle.

False Detection

While a false positive is a testing result that flags a vulnerability when it doesn’t exist, a false negative shows the result of the absence of a vulnerability when it exists. No method, whether DAST or SAST, is completely perfect when it comes to false positives and negatives.

Since SAST reviews the source of an application to identify vulnerabilities, it is likely that it can misinterpret some code. Hence, it is possible that SAST can wrongly indicate a vulnerability. On the other hand, the DAST method can result in more false negatives.

DAST tests an application when it is running and is likely to produce lower false positives than SAST. It provides a realistic view of potential vulnerabilities because of testing applications in the running state. However, DAST is not able to detect security weaknesses that are deep inside or occur in particular circumstances.

Technology Dependency

Since SAST evaluates the source code to identify vulnerabilities, it is technology-dependent for security testing. Hence, different SAST tools support different programming languages and frameworks. It scans applications when they are not deployed or executing. This requires compatibility with the respective source code technologies.

Moreover, DAST can be used to test any kind of application regardless of the underlying technologies. Hence, it is a more feasible security testing model and helps you identify vulnerabilities conveniently. No matter what framework or programming language is used with your application, DAST can test it.

Depth of Testing

SAST analyzes an application’s source code deeply and discovers vulnerabilities that open exposures from the bottom. It offers a comprehensive insight into the code and detects holes that can compromise the application’s security.

DAST, on the other hand, scans the entire attack surface of an application. It discovers vulnerabilities that can arise due to the interactions of different parts of the application. It can help to detect different types of attack patterns and provides a comprehensive view of security.

SAST vs DAST: Let’s Understand the Advantages and Limitations

You have got answers to “What is DAST?” and “What is SAST?” You have also gone through the comparison between these two methods. But as the great proverb says, you cannot judge a book by its cover, it is essential to also look at the merits and demerits of each of these security testing methods for better decision-making. Hence, let’s finish it with their advantages and limitations below.

Advantages of SAST

• It enables developers to detect vulnerabilities at the early stages of a software development process, which reduces cost and effort.
• SAST thoroughly analyzes the source code of an application, providing great insight into its inner workings and structure to detect potential vulnerabilities.
• Integrating SAST tools with development tools helps to discover potential security weaknesses as the code is written.
• You can identify flaws in design and architectural vulnerabilities with this testing method that are hard to detect during runtime testing.

Limitations of SAST

• Since SAST tools are focused on static code analysis, they fail to effectively detect vulnerabilities arising during the runtime like configuration errors.
• SAST tools produce more false positives and flag a vulnerability when it doesn’t exist.
• SAST may not be feasible for legacy applications as it requires access to the source code.

Now, let’s look at the advantages and limitations of the DAST security testing method.

Advantages of DAST

• DAST offers more authentic tests by simulating cyberattacks that provide insight into how the application behaves in real-world situations.
• It is a reliable method to discover runtime vulnerabilities, including server misconfigurations, session management issues, and more.
• It can easily scan applications for vulnerabilities as it doesn’t require access to the source code and is not dependent on technology.

Limitations of DAST

• Since a testing expert evaluates an application from an outside context in DAST, he/she doesn’t understand internal logic.
• It fails to detect vulnerabilities that require an understanding of the data flow, dependencies, and internal behavior.
• DAST can identify vulnerabilities only in live or running instances of applications and cannot work on those in the development stages.

Final Note

In most cyberattacks, unaddressed security issues are the main reasons. They are hidden holes that allow cybercriminals to gain unauthorized access to systems and applications. Hence, organizations are paying more attention to these kinds of security risks. Identifying and resolving vulnerabilities is a strong step towards a secure digital landscape.

You need the right vulnerability scanner to discover vulnerabilities accurately. DAST and SAST are two reliable vulnerability scanning methods to discover software application vulnerabilities. While SAST can uncover potential vulnerabilities from the coding level, DAST can discover vulnerabilities by simulated attacks. Each of these methods has its own significance.

Therefore, modern development teams leverage the combined power of both these security testing methods to produce highly secure software applications. You can also benefit from both SAST and DAST by integrating them into your SDLC.