Static vs. Dynamic Application Security Testing - What’s the Difference?

 There’s no need to highlight the importance of data and web application security in a day and age where most businesses depend on them entirely for their success. However, the reality of data breaches and cyberattacks is still the norm and firms need to engage in better security practices through application security testing, specifically static and dynamic application security testing (DAST) among others. 

Most businesses fail to resolve the simplest and most visible vulnerabilities on their platform, leading to loss of revenue and reputation as an impact of such hacking attempts. This is why including security methodologies such as static and dynamic application security testing throughout the software development lifecycle (SDLC). However, there are some key differences between both strategies which imply they need to be used at the right place and the right time for maximized results. 

5 Differences between Static and Dynamic Application Security Testing

As part of the application security testing (AST) strategy, SAST and DAST serve their specific responsibilities for detecting security vulnerabilities and protecting the web application from various hacking attempts. Simply put, the SAST method is similar to the white-box penetration testing methodology while the DAST method finds resonance with the black-box penetration testing methodology. The former is best suited for analyzing the source code for coding flaws, SQL and cross-site scripting injection attacks, and other misconfigurations. On the other hand, the latter looks out for vulnerabilities that pop up when the application is running to use them for external attacks. 

Other key differences between both testing approaches are:

1. Access to the source code

The SAST methodology doesn’t require a deployed application and just requires access to the source code or the binary without execution. DAST methods are used to test a running application and therefore is based on the execution phase and not accessing the source code. 

2. Costs for fixing vulnerabilities discovered

The vulnerabilities discovered during the SAST phase are in the earlier phase of the software development lifecycle (SDLC) which means that lesser time, effort, and monetary resources are required for their remediation. Under the DAST approach, the discovery of vulnerabilities is pushed towards the end of the cycle and remediation is usually pushed towards the next cycle which tends to cost more. Only the critical vulnerabilities that are in need of immediate remediation get fixed on priority. 

3. Vulnerabilities during run-time

This is one of the main differences between the SAST and DAST approaches wherein the former is unable to discover security issues when the application is running since its main focus is on the analysis of the static code. Meanwhile, as the name suggests, dynamic application security testing is specifically garnered towards detecting run-time and environment-related security problems. 

4. Support of software

The SAST methodology is flexible towards supporting different kinds of software including web applications, thick clients, and other web services. The DAST approach is limited to scanning web applications and web services and doesn’t provide a lot of use for other kinds of software. 

5. White-box vs. black-box

Also another main point of difference, SAST adopts the white-box pentesting ideology since the testing team needs access to the source code, the application framework, its design, and implementation procedure. It attempts to simulate internal attack scenarios which provide a developer perspective. The DAST approach simulates the black-box pentesting methodology as the tester formulates attack scenarios from outside the application with very little knowledge about the application infrastructure, framework, and other technologies. It tends to take on the perspective of a real-time hacker, looking for vulnerabilities that can be exploited for breaching the application.

Static and Dynamic Application Security Testing - Are They Best Combined?

Both the SAST and DAST methods cover different aspects of the application’s security which means that the best security strategy should include a combination to get the best of both. Most DAST tools provide more than just dynamic testing, such as identifying vulnerabilities on networks and devices, which allows them to tackle more than one objective. 

● SAST tools - Along with the testing of the application during its run-time, it’s crucial to gain insights into its internal security through an analysis of the source code. This is also referred to as interactive application security testing (IAST) and it combines the white-box nature of SAST with the black-box pentesting method of DAST for finding errors in both the source code and the functionality of the application (including the third-party components). 

● Vulnerability scanners - DAST tools have the provision of scanning for vulnerability but this is usually limited to web applications. In contrast, general vulnerability scanners usually have a wider scope with diverse features such as risk assessment, vulnerability management, and continuous monitoring. These are often compared or contrasted with automated pentesting tools.

Both static and dynamic application security testing approaches have their strengths and weaknesses but this doesn’t necessarily mean that they are competing methods. In a combined approach, they can find a great number of vulnerabilities and find their own utility at different phases of the SDLC.

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