DAST vs. SAST: Fact-checking static and dynamic application security testing


What is DAST and what is SAST?

To eliminate definitions, dynamic application security testing (DAST) is a black box testing methodology in which a running application is tested from the outside. A DAST tool explores the application and probes for runtime vulnerabilities, just like an attacker would. On the other hand, static application security testing (SAST) is a white-box security testing method that inspects application source code to identify potential security vulnerabilities.

So, in a nutshell, DAST verifies a running web application while SAST verifies its static code.

What is IAST, then?

Interactive Application Security Testing (IAST), sometimes referred to as gray-box testing, fall somewhere between dynamic analysis (white-box testing) and static analysis (black-box testing). Depending on the vendor, IAST can be a standalone security testing tool that adds dynamic testing capability to SAST or a way to add source code information to dynamic testing. For Invicti specifically, IAST is implemented as a server-side agent that constantly communicates with the main vulnerability scanner to find more than DAST alone could (more on that later).

SAST vs DAST Coverage in Web Application Security Testing

Coverage is a fundamental attribute of security testing, both within a specific application and across your web application environment. To accurately assess the security of an application, your security testing solution must know what to test and how to interpret the items it finds in your application.

SAST operates on application source code, so you need to have that code with tools that support a specific programming language and web application framework. For several different technology stacks, this may mean several SAST tools. In a broader context, SAST coverage is usually limited to applications under active in-house development, because you need both the code and the right test toolchains. So while you may hear opinions that only SAST provides full testing coverage because it tests all code, this is only true for a specific application’s code base and the limited subset of risks. security that can be statically detected.

DAST tools such as vulnerability scanners, on the other hand, are technology-agnostic because they externally test applications and examine their behavior, not their source code. This allows DAST to cover any number of applications, regardless of technology stack, development status, or source code availability, testing anything externally accessible to a visiting browser. . Leading dynamic scanners can identify a wide range of vulnerabilities, including misconfigurations and other runtime issues. They also support modern authentication schemes to access sections of the site and features available only to authenticated users.

Web API Security Test

Web application programming interfaces (APIs) are the cornerstone of the cloud and the guardians of the data provided by web services. Performing security testing on API endpoints is now a critical requirement to prevent data breaches – and it’s primarily a job for DAST and manual penetration testing.

Get the Invicti White Paper at API security testing to find out why this is a crucial part of web security.

Accuracy and efficiency of security testing with SAST vs DAST

False positives are always a hot topic in application security testing, understood as both erroneous results and valid but not actionable results. SAST tools, in particular, have a reputation for flooding developers with security issues that, while technically accurate, are not relevant in a specific context. This requires careful tuning to prevent developers from being inundated with false positive reports that consume their time without any security benefit and, in fact, are routinely ignored.

The big advantage of DAST is the ability to identify actual exploitable vulnerabilities rather than just pointing out potentially insecure code constructs. While some early DAST tools struggled to deliver on this promise, industry leaders modern DAST solutions rely on evidence, no suspicion, and some can even automatically confirm exploitability to flag high-priority issues. This makes DAST the ideal approach for time-strapped development teams, allowing them to focus on patching the vulnerabilities that really matter.

Find vulnerabilities with DAST and SAST

To give a specific example, suppose an application retrieves data from an SQL database based on user input from a web form. A SAST tool can identify the source code fragment that does this and warn the developer that the SQL query in a specific line of code is assembled in an insecure manner and could potentially lead to a SQL Injection (but maybe not). A DAST tool will find the web form on a page and run security checks to simulate real SQL injection attacks. If any of the test attacks are successful, the scanner will report that the application has an SQL injection vulnerability on that specific page:

So the difference between SAST and DAST results is the difference between “we should probably look into this” and “we need to fix this now” – especially important for weaknesses like cross-site scripting (XSS), where many suspicious code constructs will never lead to an actual exploitable vulnerability.

The quality of DAST tools varies widely, but any decent DAST should also identify out-of-band vulnerabilities – security weaknesses that don’t give immediate reactions to security checks. Invicti uses its built-in Hawk component to listen for traffic that reports out-of-band and second-order vulnerabilities such as XX:

Integrate SAST and DAST into your SDLC

Security testing at the earliest stages of your software development life cycle (SDLC) is crucial to finding and fixing vulnerabilities before they reach later stages or even production. Source code analysis is the most natural way to find and eliminate security flaws in the early stages of development. SAST is generally easy to integrate into development environments and workflows, whether as an IDE checker or a standalone analysis process. However, since SAST cannot identify runtime vulnerabilities and misconfigurations, some form of dynamic testing is still required in the SDLC.

Regardless of some long-standing misconceptions, DAST tools can (and should) also be integrated into the SDLC. While it’s true that DAST can only be performed on a deployed application, most modern web frameworks can automatically generate code for prototyping at any stage of development to reduce clutter. The big advantage is that DAST can run at multiple stages of the SDLC, from partial testing in development to full testing in staging and even production testing by security teams. Since DAST checks the entire application for vulnerable behaviors and responses, regardless of the implementation details, this is the recommended starting point for add security tests in the SDLC.

The Invicti method: DevSecOps with DAST+IAST+SCA

With all the acronyms in AppSec, it’s easy to get sucked into choosing one AST approach over another or (even worse) checking boxes to make sure you get all the acronyms, preferably in a set. The ultimate goal, however, is not to fill a shopping list, but to find a way to secure your web applications and keep them safe. The path to get there is different for every organization and rarely quick or easy. At Invicti, we’ve developed a fast-track approach that leverages the truly unique capabilities and feature combinations of our products.

The Invicti solution is built around the industry’s most mature DAST platform and uses Proof-Based Scanning to automatically confirm the vast majority of high-impact exploitable vulnerabilities without the risk of false positives. These confirmed results can be sent directly to developers through out-of-the-box integrations with issue tracking tools and CI/CD pipelines to ensure application security can keep up with deep automation of DevOps development processes . Each vulnerability report includes detailed remediation guidance, and each patch can be automatically retested, allowing organizations to implement a zero-touch AppSec process that doesn’t interfere with development and leads to more secure code in the long run.

The main DAST engine can be supplemented by an IAST tool with additional software composition analysis (SCA) capabilities. With a Invicti IAST agent installed on the web or application server, you can get more detailed scanning and scanning results, more vulnerability confirmations, and SCA checks to detect vulnerable open source dependencies. IAST agents are currently available for PHP, .NET, Java, and Node.js, with more in development.

The post office DAST vs. SAST: Fact-checking static and dynamic application security testing appeared first on Invicti.

*** This is a syndicated blog from the Security Bloggers Network of Invicti written by Zbigniew Banach. Read the original post at: https://www.invicti.com/blog/web-security/dast-vs-sast-fact-check-on-static-and-dynamic-application-security-testing/


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