Application security testing is crucial to ensure the code is resilient to vulnerabilities. When it comes to choosing the correct methodology to application security testing the SAST Vs. DAST debate gets sparked. Both the SAST and the DAST approach detect different types of vulnerabilities. This article intends to build an understanding of when to adopt which.
What is SAST?
SAST or Static Application testing is a white box approach to testing where the code is tested before compilation and in a static state. SAST involves scanning the source code of a program to pinpoint potential security vulnerabilities. These vulnerabilities range from SQL injection, buffer overflows, XML external entity (XXE) attacks, and other high-priority security risks outlined in the OWASP Top 10.
The SAST approach is a test driven development approach that directs developers to initiate security testing during the initial stages of application development, without executing functional components. This proactive method uncovers security flaws in the application’s source code early in the development process, saving from glitches while running the code.
The Advantages of SAST
The most significant advantage of SAST is to pinpoint an issue by marking its location including file name and line number. The SAST tools also provide a brief description of the issue and rate the severity of the issue. SAST comes with an immediate benefit of not requiring to build a small functioning component. This actually helps in saving cost and development time. Detecting problems early also makes it easier and cheaper to fix them.
What is DAST?
DAST functions as a closed-box testing method, mirroring the perspective of an external attacker. It operates under the assumption that the tester lacks intricate knowledge of the application’s internal workings. Unlike SAST, DAST can detect vulnerabilities that manifest only during program runtime.
Dynamic Application Security Testing (DAST) involves real-time scanning of software applications against leading vulnerability sources like OWASP Top 10 or SANS/CWE 25, attempting to identify security flaws and vulnerabilities.
The Advantages of DAST
DAST spots a range of real world vulnerabilities like memory leaks, cross-site scripting (XSS) attacks, SQL injection, and authentication and encryption issues. DAST checks both the internal state and external environment of the application. This property empowers DAST to test various API endpoints, web services that the application interacts with. It also tests the integration with cloud, data lakes, or other hosting infrastructure with the application.
Comparing SAST Vs. DAST
When we analyze the properties of SAST and DAST we find some key differences in their scope of implementation like:
White box Vs. Black box
While SAST is used for white box testing the DAST takes a black box testing approach. In white box testing the tester gets access to underlying framework and design. The application is tested from inside out in a developer approach. DAST on the other hand takes a hacker approach to test the system from outside in.
Requirements
SAST can work in an application before deployment and only the source code is enough. DAST on the other hand needs a working version to perform external testing without, requirement of source code here is immaterial.
Stage of SDLC
SAST finds vulnerabilities in the early stages of SDLC. Often the findings are fixed before even entering the QA stage in the preemptive approach of SAST. DAST is for detecting critical vulnerabilities during emergency release and takes place towards the end of the SDLC
Scope
SAST supports testing of all kinds of software while DAST is restricted to scanning apps like web apps and webs services. SAST uses a wide range of static inputs for scanning like documentation, design specification, and application source code.
Combining the Good of SAST and DAST
Both SAST and DAST find their use cases in detecting different types of vulnerabilities and fulfills a security program when working together.
One testing methodology is not inherently better than the other though SAST might seem a better choice as it performs in the earlier part of software development.
Employing a combined approach that integrates both SAST and DAST scanning tools broadens the scope of vulnerabilities and exploitable weaknesses you can uncover, amalgamating the advantages of SAST’s static analysis with DAST’s dynamic approach to security testing.
Integrating other security testing forms, such as Interactive Application Security Testing (IAST) and Runtime Application Self-Protection (RASP), can further fortify your application’s security.
