SAST vs. DAST for Security Testing: Unveiling the Differences

Application Security Testing (AST) encompasses various tools, processes, and approaches to scanning applications to uncover potential security issues. Static Application Security Testing (SAST) and Dynamic Application Security Testing (DAST) are popularly used security testing approaches that follow different methodologies of scanning application codes across different stages of a software development lifecycle.  

SAST follows a white-box testing approach to analyze the binary code to identify exploitable vulnerabilities and coding errors. On the other hand, DAST implements a black-box testing method, where security engineers parse simulated attack payloads through the application’s front end without exposing internal information on the application’s internal construct.  

In this blog, we will discuss SAST and DAST testing approaches, how they help detect vulnerabilities and application failures, their differences, and best use cases. 

Static Application Security Testing (SAST) 

SAST tools offer immediate feedback on application flaws introduced during the code development process. As it operates in the early stages of the SDLC, it helps to identify coding errors before software compilation. It aligns seamlessly with a DevSecOps shift-left approach, supporting a proactive security approach. 

Common vulnerabilities detected by SAST include: 

• Buffer overflows 

• Cross-Site Scripting 

• SQL injection 

Benefits of SAST Scans 

Early Vulnerability Detection: Launched at the beginning of development, SAST detects vulnerabilities before code is released, supporting proactive remediation and mitigation of security flaws. 

Real-time Feedback: SAST scanners perform rapid scans and can analyze the entire code base of an application in a shorter duration. Apart from providing instant feedback on the uncovered flaws, SAST tools seamlessly integrate with various development pipeline tools without impacting core functionalities. 

Accuracy: SAST tools perform security tests automatically based on predefined security rules. These tools identify critical vulnerabilities faster and more accurately than manual testing approaches. 

While SAST promotes secure coding practices, its scope is limited in that it is unable to identify runtime vulnerabilities, which is what brings us to DAST. 

Dynamic Application Security Testing (DAST) 

Unlike SAST, Dynamic Application Security Testing evaluates the application using an outside-in approach by simulating the actions of a malicious user to orchestrate attacks. DAST scans operate by entering suspicious user inputs and observing the application’s response to evaluate runtime vulnerabilities.  

The testing mechanism continuously scans web applications deployed in production, helping simulate the application’s real-world behavior and identify issues affecting the typical user experience. Since DAST tests are performed in a runtime environment, security engineers can also detect and identify new vulnerabilities as they arise and evolve. 

Vulnerabilities uncovered by dynamic analysis include: 

• Cross-Site Request Forgery 

• File inclusion vulnerabilities 

• Cookie manipulation 

• Path disclosure vulnerabilities 

• Memory corruption 

• Injection flaws 

Benefits of DAST Tests   

Language Agnostic: DAST tests do not require knowledge of the programming languages used to develop the application. DAST tools evaluate the application’s behavior based on inputs and outputs no matter the frameworks used, making it a more robust testing approach. Since they are built to be language-agnostic, DAST tools enforce seamless collaboration between development and security teams for easier security risk management. 

Low Rates of False Positives: DAST tools perform end-to-end scanning of the application environment, enabling security researchers to detect and identify security flaws that threaten the application’s security and functionality. 

No Binary Code Access Required: DAST scans, performed through the application's front end, allow third-party security services to conduct tests without exposing the application code. 

The Difference Between SAST and DAST  

While both SAST and DAST follow proactive vulnerability identification approaches, they possess different strengths suitable for diverse use cases. The following section outlines the differences between the two technologies and factors to consider when selecting the right application security tool. 

SAST is essential in modern software development lifecycles, detecting critical vulnerabilities before they reach the production environment. As a best practice, SAST tools are recommended to be used by developers to help them identify and detect coding errors while they are writing the software. SAST is also appropriate for root cause analysis, which helps determine the exact location of the problem within lines of code after other vulnerability scans have detected flaws. 

Combining SAST and DAST Scans for Optimum Results  

Since they offer varying strengths, DAST and SAST complement each other and are best used together for implementing a much more robust testing approach. A practical method is to adopt SAST tools early in the code development stage, enabling comprehensive security analysis of all functionalities and packages used for the application. Then, the binary code and dependencies can further be loaded into a staging environment where security engineers can perform DAST tests to assess how attackers can exploit vulnerabilities in production. 

DAST finds vulnerabilities that cannot be discovered by SAST: 80% of web applications have a critical vulnerability that can only be found with a dynamic scan. 

For deployed applications, DAST can identify new vulnerabilities, while SAST scans target vulnerable components to determine the root causes of a vulnerability. 

Streamline Security with SAST and DAST in One Platform  

Development teams use several tools collectively to reduce the burden of administering DAST and SAST tests. These tools operate on a set of security rules to automate the discovery, identification, and remediation of security vulnerabilities. The Veracode Intelligent Software Security Platform streamlines this process, offering a single, cloud-native platform that saves time and budget on threat modeling, automating tests, and providing actionable reports on discovered vulnerabilities. 

To see how Veracode can eliminate security blind spots and help you find and fix flaws before they become targets for a breach, try our Dynamic Analysis security solution free today.