What are DAST, SAST, & IAST and How Do They Impact Mobile App Security?

Recent research found that consumers in eight major global markets spend over five hours per day using mobile apps. In the first quarter of 2023, users downloaded 27 billion apps from Google Play. As mobile app usage grows, both users and publishers expect a high level of app security. After all, the theft of intellectual property and risk of losing revenue and reputation in an attack are serious consequences.

To ensure that your mobile app is secure, it’s important to integrate a comprehensive security strategy throughout the development process, not just at the end. This includes performing mobile application security testing (MAST).

MAST refers to the process and tools used to identify potential security issues in your mobile app. MAST can help you find issues that need to be fixed in your application before they can be exploited by a threat actor and negatively impact your business.

Let’s examine the most common MAST types: Static Application Security Testing (SAST), Dynamic Application Security Testing (DAST), and Interactive Application Security Testing (IAST). Plus, we’ll explain how each type plays a crucial role in ensuring that your application is secure.

What is SAST?

SAST analyzes your application in a non-running state, specifically evaluating the source code, bytecode, or binary code. Implementing SAST helps identify security issues, weaknesses, and potential flaws in your application, ensuring that you’re able to correct them before publishing the app. SAST should be performed early on and throughout the development process. Doing so can highlight flow and structural issues while they’re easier to correct. Delaying or failing to perform SAST can potentially allow serious flaws to persist in your mobile app. Correcting them at the end of the development process is often costly, time intensive, and can result in delays in app publishing schedules.

What is DAST?

Unlike SAST, which tests your app by analyzing the code and structure in a non-running state, DAST tests in a running state. This type of MAST executes your mobile app and examines it as it would run on a real device, giving you an end-user’s perspective of app functionality.

DAST evaluates resources and checks for security mechanisms that can’t be recognized prior to running your app such as:

• Disclosure of data in transit.
• Authentication and authorization issues.
• Server misconfigurations.
• Dynamic application behavior.

Because DAST checks compiled code in a runtime environment, it’s usually performed near the end of the software development lifecycle (SDLC).

DAST is helpful for viewing your app from an attacker's point of view — with no inside knowledge of your app’s source code — and spotting vulnerabilities prior to production. Depending on the vulnerability’s level of severity, you may decide to address the vulnerability prior to publishing or push until the next app release.

What is IAST?

IAST is a dynamic application security testing approach that combines elements of SAST and DAST. While the app is running, IAST performs testing via instrumentation, or software libraries, added to the application’s code. The additional monitoring functionality actively observes your mobile app’s behavior and interactions during runtime.

IAST is often performed later in the SDLC around the testing/QA phase. The instrumentation is able to access:

• Code
• Dataflow and control flow
• System configuration data
• Back-end connection data

A unique benefit of IAST is that it identifies where in your code a vulnerability exists, like SAST, but does so in the runtime environment, like DAST. When vulnerabilities are detected by DAST, there’s not necessarily detailed information to help developers pinpoint the issues. IAST, however, provides detailed information, similar to SAST, to help developers find and fix issues faster.

What type of testing should you use?

SAST should always be performed throughout the software development lifecycle — this helps find potential vulnerabilities as early as possible and is a very efficient type of testing.

IAST is growing in popularity as it provides real-time feedback on your mobile app’s vulnerabilities. While you should consider implementing IAST, it’s usually run during the testing/QA portion of the SDLC, which misses crucial testing periods earlier on in your app’s development lifecycle and requires a greater level of effort.

Because of this, implementing both SAST and IAST is considered a best practice. SAST evaluates your application early on and throughout the development process enabling you to find and fix logic and structural errors before they become widespread and difficult to correct. IAST should be used later in the process, in a real or simulated runtime environment to pinpoint and correct errors prior to publishing your app.

The importance of MAST

The importance of MAST as part of a comprehensive mobile application security strategy cannot be overstated. Implementing MAST throughout your app’s SDLC can help you find and fix serious errors, improving the security posture of your app and preventing potential attacks.

While MAST can be performed manually, automating the process can save your team time and money, while improving accuracy. Guardsquare’s free MAST product, AppSweep, integrates seamlessly into your app’s development process, and offers robust SAST and IAST testing throughout the development process. AppSweep maps its findings to the OWASP Mobile Application Security Verification Standard (MASVS) and provides actionable security recommendations — helping you view and fix vulnerabilities faster. The result is maximized security with minimal disruption to your development workflows.

• Mobile app security testing (MAST) is crucial for finding and fixing errors in your app prior to publication.
• SAST, DAST, and IAST are common MAST techniques that can be integrated into your app early on and throughout the software development life cycle (SDLC). Guardsquare recommends using both SAST and IAST to test your app prior to code compilation and in a runtime environment.
• MAST can be done manually, but it’s best to opt for an automated testing tool like AppSweep. AppSweep automates SAST/IAST testing, maps the findings to OWASP’s Mobile Application Security Verification Standard (MASVS), and provides actionable recommendations for vulnerability correction.