Application testing in Software Development Life Cycle (SDLC) has improved significantly from the less iterative waterfall approach. As the modern world gets more code-dependent, organizations face a hard time developing good software while meeting high reliability and security demands.

Owing to the complexity of software applications, most organizations today tend to ignore the critical role of Software Composition Analysis tools in open source security. This is often contributed by the misconception that SAST and DAST, among other security tools, can be used to detect vulnerabilities and flaws in open source components, which is wrong.

If you’re wondering which security testing paradigms to use between SAST, DAST, and SCA, or  whether to employ them all, this post is yours. Hang on as we compare what each tool does, and its role in keeping your applications secure and reliable.

Static Application Security Testing (SAST)

SAST is a white-box testing methodology. A white-box security tool analyzes your application’s source code or binaries to identify security vulnerabilities and flaws that might otherwise be baked into the code during compilation.

Static Application tools employ an inside-out testing approach to analyze the application during the early stages of the application life cycle. It takes place before the application is implemented, as it does not require it to be working.

A Static Application Security Testing tool does not necessitate you to execute the code. However, some lightweight SAST tools can be employed at any stage of the SDLC, including the coding phase. Others can also be used when the code is ready to be compiled.

The Role of SAST in Application Security

The critical role of static analysis tools is to monitor and ensure continuous code quality. It does this not only in the early stages of SDLC but also in the maintenance phases. This helps the organization lower the potential risks and costs that might arise due to unforeseen application security and reliability issues.

Because SAST tools are implemented during the development phase, they are critical in detecting security-related issues in real-time. The significant benefit here is that problems are fixed there and then as opposed to being passed on to the next development phase.

Benefits of SAST

  • Detects vulnerabilities in the very early stages of coding- detecting flaws in the early phases protects the organization from high remediation costs that may be accrued in case a security-related issue is seen after the software has been implemented or after an attack.
  • Guarantees continuous code quality and security- while SAST is done before the coding stage, its benefits are manifested long after establishing the security baseline and initial code quality. After writing a new code block, the SAST tools scans it and offers real-time feedback on any vulnerabilities that need to be fixed before the code can be implemented into the build system.
  • Another benefit of SAST is to detect complex vulnerabilities that are difficult to identify before accessing the source code.
  • The SAST tool can tell the developers the precise vulnerability location, which helps manage false positives and simplify remediation.

Drawbacks of SAST security tools

  • With some of these tools, the code needs to be compilable. This issue is even worse, especially when the developer can’t access the necessary libraries and instructions to compile it.  
  • These tools often produce lots of false positives and false negatives.
  • They can’t detect particular vulnerabilities automatically during the early stages, including weak cryptography and access control issues.
  • More applications and developers utilizing these tools lead to a pile-up of unclear issues and false positives and negatives.

Dynamic Application Security Testing (DAST)

DAST is a black-box testing methodology. Unlike SAST that takes an inside-out approach, DAST tests the security of an application from the front-end.

Put, in other words, it involves simulating attacks to the application like a hacker would do to identify security vulnerabilities.

Unlike SAST, DAST tools don’t have access to the source code. This is because they detect security risks by performing attacks on the application’s HTTP and HTML interfaces.

These tools are named ‘dynamic’ because they test the application from a dynamic environment. Importantly, although DAST can be done during production, testing is often carried out in a testing environment. This makes it easy to detect vulnerabilities that can only be seen externally.

Benefits of DAST

  • Good at identifying configuration issues.
  • DAST does not require source code, so it’s possible to run in different applications without language limitations.
  • Has comparably low false positives.

Drawbacks of DAST

  • It heavily relies on experts to formulate the tests. This makes scaling difficult.
  • Experts need security knowledge to interpret the results.
  • DAST scans for vulnerabilities after production. Thus, fixing the issues becomes costly and time-consuming.

Can SAST and DAST replace SCA?

As it turns out, each of these 3 AST tools focuses on different but critical application security aspects. While SAST detects flaws and vulnerabilities during the early stages of application development, DAST tests the software’s reliability and security from a malice user’s position.

On the other hand, SCA tools perform a completely different task but still within the application security department. SCA is relatively new in the application security testing market. It came up as a result of a cross-industry increase in the usage of open source components.

The wide use of open source made it necessary to intuitively manage these external components. That said, the primary role of Software Composition Analysis tools, such as Snyk, is to make an inventory of all the open-source components that you have incorporated in your projects.

These tools will offer necessary information regarding open source components and any vulnerabilities discovered so the developers can fix them quickly.

At the end of the day, no AST tool is superior or inferior to the rest and none should be left out when securing an application or web software . Considering that they detect vulnerabilities from different angles, SAST, DAST, and SCA will offer better value if they are treated as complementary tools.

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