DAST vs. SAST: 5 Key Differences and How to Choose

Decoding Application Security Testing: A Critical Comparison of DAST and SAST

In the specialized field of application security testing, the debate between Dynamic Application Security Testing (DAST) and Static Application Security Testing (SAST) remains a focal point. As applications become increasingly complex and integral to business operations, ensuring their security is paramount. This article aims to dissect and compare these two prominent approaches to application security testing. While both DAST and SAST are designed to identify vulnerabilities, their methodologies, effectiveness, and implementation vary significantly. We'll delve into how each method functions, their respective advantages and limitations, and the scenarios in which they excel. By providing a 5 key differences, this guide seeks to empower developers, security engineers, and decision-makers with a clearer understanding of DAST and SAST. This will enable you to choose the most appropriate testing strategy for your applications, ensuring robust security in a world where digital threats are constantly evolving. As we conclude, special attention will be given to the evolving landscape of API security testing, highlighting its growing importance and how DAST and SAST relates to this critical area.

This is part of a series of articles about Application Security Testing

What Is DAST (Dynamic Application Security Testing)? 

DAST, or Dynamic Application Security Testing, is a process that involves testing an application during its running state. It is a black box testing technique, which doesn't require access to the source code of the application.

The primary aim of DAST is to identify security vulnerabilities that could be exploited during the application's runtime. It seeks to simulate attacks from an attacker's perspective and identify potential weaknesses that could be exploited if left undetected. Some of the common vulnerabilities that DAST can uncover include Cross-Site Scripting (XSS), SQL Injection, and security misconfigurations.

Learn more in our detailed guide to dynamic application security testing

DAST tools can test any application, regardless of the programming language used. It's primarily focused on the exposed HTTP and HTML interfaces of an application, which makes it particularly effective in identifying vulnerabilities that could be exploited via the web.

Tzvika Shneider

CEO, Pynt

Tzvika Shneider is a 20-year software security industry leader with a robust background in product and software management.

Tips from the expert

• Understand your testing needs: Evaluate your project requirements to decide whether a more comprehensive, dynamic approach (DAST) or a code-level focus (SAST) is appropriate.
• Combine SAST and DAST for complete coverage: Use both testing approaches in tandem to cover vulnerabilities in both the codebase and runtime environment.
• Implement immediate remediation workflows: Establish remediation workflows that trigger upon vulnerability detection, ensuring swift action regardless of the testing method used.
• Integrate security testing into development phases: Whether using SAST or DAST, integrate testing within the development process to catch and fix issues early on.
• Continuously educate developers on SAST and DAST findings: Use findings from both testing methods to educate developers about common vulnerabilities and best practices to avoid them.

Why Is DAST Important? 

Cyber-attacks are growing both in frequency and sophistication. DAST provides a real-world perspective of how an application can be exploited during its runtime. By simulating attacks, it uncovers vulnerabilities that could be missed by other testing techniques. It gives developers a clear understanding of the potential threats their application could face and enables them to take proactive measures to mitigate them.

Moreover, DAST is language-agnostic. This means it can be used to test any application, irrespective of the programming language or framework used. This gives it a broader scope and makes it a versatile tool for ensuring the security of diverse applications.

DAST can be integrated into the CI/CD pipeline, enabling continuous security testing. This ensures that runtime security issues are detected during testing stages, and remediated before they reach production environments.

Related content: API Security: Threats, Tools, and Best Practices

What Is SAST (Static Application Security Testing)?

Static Application Security Testing (SAST) is a testing technique that involves analyzing the source code of an application without actually executing it. It is a white box testing technique, which requires access to and understanding of the codebase and the underlying programming language.

SAST is designed to identify potential security vulnerabilities that could be present in the code. It does so by checking the code against a set of predefined rules or patterns associated with known security vulnerabilities. Some of the common security issues that SAST can uncover include buffer overflows, insecure encryption algorithms, and unhandled exceptions.

One of the key advantages of SAST is that it can be performed early in the development cycle, even before the code is compiled. This allows developers to detect and fix security issues right at the development stage, thereby minimizing the risks and costs associated with them.

Why Is SAST Important? 

SAST allows for early detection of vulnerabilities. Since it can be performed right at the onset of development, SAST enables developers to identify and rectify security issues before the code is even compiled. This saves time and effort and also significantly reduces the costs associated with fixing security issues later. 

SAST provides a deep-dive analysis of the code. It scans the entire codebase, including the libraries and frameworks used, to identify any potential security flaws. This ensures comprehensive coverage of all aspects of a software program, including third-party libraries and packages. 

With the advent of DevSecOps, security has become an integral part of the development lifecycle, and SAST fits well into this paradigm. By automating SAST scans, developers can ensure that security is a key consideration right from the start of the application lifecycle.

SAST vs. DAST: 5 Key Differences  

1. Stage of Implementation

SAST is performed early in the development lifecycle, even before the code is compiled. It involves analyzing the source code, byte code, or application binaries to identify vulnerabilities. This allows developers to detect and fix vulnerabilities early in the development process, which can save time and resources.

On the other hand, DAST is performed after the application has been developed and is in its running state. It involves testing the application from the outside, and simulating the actions of an attacker to find vulnerabilities. The advantage of DAST is that it can identify vulnerabilities that are only visible when the application is running, including those that may have been missed during the SAST stage.

2. Nature of Testing

SAST focuses on the internal structure of the application, examining the source code, design, and architecture to find potential vulnerabilities. It's a thorough and meticulous process that can detect a wide range of vulnerabilities, from input validation issues to buffer overflows.

On the other hand, DAST focuses on the external behavior of the application. It tests the application's interfaces, HTTP and HTML interfaces, server-side scripts, and more to find vulnerabilities that can be exploited by attackers.

3. Vulnerabilities Detected

SAST can identify vulnerabilities related to the code and architecture of the application, such as insecure coding practices, use of insecure libraries, and buffer overflows. It's also capable of detecting vulnerabilities in the early stages of development, making it an invaluable tool for developers.

DAST excels at detecting vulnerabilities that are only visible when the application is running. This includes vulnerabilities related to the runtime environment, such as insecure server configurations, vulnerabilities in third-party components, and flaws in the application's interaction with other systems.

4. Depth vs. Breadth

SAST provides a deep, thorough analysis of the application's code and architecture, but it may not cover all the possible runtime scenarios. It's excellent for identifying vulnerabilities in the code, but it may not detect all the vulnerabilities that can be exploited at runtime.

DAST provides a broad, surface-level analysis of the application's behavior at runtime. It can detect a wide range of runtime vulnerabilities, but it may not provide as deep an analysis as SAST. It's excellent for identifying vulnerabilities that are visible at runtime, but it may not detect vulnerabilities in the code or architecture.

5. API Security Testing

Securing Application Programming Interfaces (APIs) is a crucial component of application security. APIs, which allow different software systems to communicate, are increasingly being targeted by attackers due to their accessibility and the sensitive data they often handle. While traditional SAST (Static Analysis Security Testing) and DAST (Dynamic Application Security Testing) can be used for API security testing, they have limitations when it comes to addressing the unique challenges posed by APIs.

SAST examines the source code of APIs without running them. SAST scans the code for patterns that could lead to security issues, such as authentication flaws, improper encryption methods, or coding practices that could leave the API susceptible to attacks like SQL injection. Since SAST analyzes the code statically, it is adept at uncovering issues in the logic that defines the API's behavior, such as how it processes requests and responses, and how it handles data.

DAST tests APIs in their running state, focusing on how the API behaves when it is operational. This approach simulates external attacks, mirroring real-world scenarios where attackers might exploit vulnerabilities that only become apparent when the API is active. DAST evaluates the API's responses to different types of requests, including unauthorized or malformed requests, to check for vulnerabilities like exposure of sensitive data, improper error handling, or security misconfigurations, including how it manages data transmission and authentication.

However, both traditional SAST and DAST tools, while valuable for certain aspects of application security testing, have limitations when it comes to comprehensively addressing API security. These tools may not fully capture the intricacies of API-specific vulnerabilities and may miss issues that are only apparent during runtime. As a result, there is a growing need for dedicated API security testing tools that can provide specialized support and a deeper understanding of the unique challenges posed by APIs.

Learn more in our detailed guide to dast tools

SAST vs. DAST: Which Should You Use? 

Choosing between DAST and SAST largely depends on your specific needs and where you are in your SDLC. If you are in the early stages of development, implementing SAST would be beneficial as it can identify potential issues at the code level. This early detection allows developers to rectify issues before they become more significant problems.

If your application is in its running state, implementing DAST can help identify vulnerabilities that become evident only when the application is operational. DAST can also be beneficial in the final stages of development when you need a real-world perspective of how your application performs under attack scenarios.

However, it's important to note that DAST and SAST are not mutually exclusive. Many organizations use both technologies, to achieve comprehensive security coverage for applications. While SAST can identify potential vulnerabilities in the code, DAST can detect vulnerabilities that are exploitable when the application is running.

Pynt - Dedicated for API Security Testing

Pynt, unlike traditional Static Application Security Testing (SAST) and Dynamic Application Security Testing (DAST) tools, offers a specialized and comprehensive approach to API security testing. While SAST and DAST tools may provide some support for API security, they often lack the depth and specificity required to address the unique challenges posed by modern APIs. Pynt, on the other hand, is purpose-built to excel in this domain.

One of the key distinctions of Pynt is its focus on analyzing response payloads rather than scanning source code. Traditional SAST tools examine the source code for patterns that could lead to security vulnerabilities, while DAST tests APIs in their operational state. Pynt, however, operates at a different level by understanding the behavior of APIs through their responses. This approach allows Pynt to uncover vulnerabilities that may not be evident from static code analysis or operational testing alone.

Moreover, Pynt's expertise extends beyond just supporting common API architectures like REST; it is adaptable to various API technologies, authentication methods, and data formats. This adaptability ensures that Pynt can effectively assess APIs regardless of their specific characteristics, making it a versatile tool for API security testing. In summary, Pynt's unique capabilities, including response payload analysis, business context awareness, and adaptability, make it a valuable addition to the API security testing toolkit, addressing the limitations often associated with traditional SAST and DAST tools.

‍Learn more about how Pynt can overcome the API security testing unique challenges