In the realm of application and API security testing, there are three primary approaches: SCA (Software Composition Analysis), SAST (Static Application Security Testing), and DAST (Dynamic Application Security Testing). These methods serve different purposes and have distinct strengths and weaknesses.

Static Application Security Testing (SAST):

SAST, or Static Application Security Testing, involves an automated analysis of an application’s written code, whether it’s compiled or uncompiled. This method dissects the code into various components for in-depth scrutiny to uncover security vulnerabilities. Unlike human assessment, SAST tools excel at delving deep into functions and subroutines, potentially identifying vulnerabilities several layers deep. While they possess this capability, SAST tools are often criticized for being slow, generating false positives, and requiring skilled experts to use effectively. Nonetheless, their advantage lies in their ability to detect a wide range of vulnerabilities, including memory leaks, endless loops, and unhandled errors. Another significant advantage of SAST is its ability to provide complete code coverage, scrutinizing every line of code in the application. However, questions arise about the necessity of complete code coverage in every application.

Dynamic Application Security Testing (DAST):

DAST, or Dynamic Application Security Testing, takes a different approach by interacting with a running application to identify and manage vulnerabilities. To use a DAST tool, the application must be running on a server, virtual machine, or container during the analysis. These tools act as intermediaries, intercepting communications between the front end (browser) and back end (server). DAST tools analyze requests and responses to learn about the application’s behavior in real-world usage. They employ features like crawling, fuzzing, and dynamic analysis to comprehensively assess the application. While DAST tools are efficient at identifying business logic and implementation problems, they cannot guarantee complete code coverage, necessitating manual verification to ensure all parts of the application are evaluated.

Software Composition Analysis (SCA):

Software Composition Analysis (SCA) focuses on verifying third-party libraries, frameworks, and components used within an application. It primarily targets the code that the development team did not create. SCA tools do not conduct static or dynamic analysis of the code within these third-party components. Instead, they rely on external sources such as the Common Vulnerability Enumeration (CVE) database, exploit databases, security researchers, vendor research, and information released by component creators. SCA tools cross-reference the application’s list of dependencies against known-vulnerable dependencies, promptly reporting matches. This approach yields rapid and generally accurate results when compared to the more comprehensive analyses of SAST and DAST.

Conclusion

In the complex landscape of application security testing, each method — SAST, DAST, and SCA — brings its unique strengths and considerations. SAST excels in deep code analysis, offering the potential to unearth a wide array of vulnerabilities, but it requires expertise to manage its output. DAST thrives in real-world testing, but it may miss some vulnerabilities and demands manual verification for complete coverage. SCA, on the other hand, swiftly identifies vulnerabilities in third-party components, enhancing software supply chain security. While no single method is a panacea for application security, combining these approaches in a multi-layered strategy ensures a comprehensive defense against evolving threats, allowing developers to craft robust and secure software.