Secure coding practices are essential for safeguarding web applications, but no code is entirely free from vulnerabilities. The most powerful way to expose these hidden threats is through thorough testing — both static (analyzing the code in its dormant state) and dynamic (evaluating it during runtime). By adopting this proactive strategy, developers can pinpoint and resolve security weaknesses early in the development process, significantly enhancing the application’s resilience against potential attacks.
Testing Your Web Applications
Static testing
First, let’s look at static application security testing (SAST). When testing an application statically, you are doing so from the perspective of the developer of the application. This means you have full access to the source code and documentation of the application, effectively giving you full knowledge of the how the application works, how data flows through the application, and where there might be a security flaw in the code (that is why this method of testing is also called white-box or transparent box testing).
Testing statically is important in the software development lifecycle (SDLC) because it catches flaws before the code has been fully written and deployed into a running environment. That translates to cost savings due to bug fixing becoming more expensive the further you are in development. But how you statically test the code is really the important question, and the answer is dependent on your needs.
To accelerate the process, many companies turn to automated static code analyzers. These powerful tools scrutinize code for potential security vulnerabilities and generate detailed reports, pinpointing issues down to the exact line of code. High-end solutions not only identify flaws but also provide guidance on remediation and seamlessly integrate into the development lifecycle, easing the burden on developers and web application security teams with automated scanning and bug tracking.
However, automated analyzers are not without their drawbacks, particularly their tendency to produce false positives. As a result, the findings must be reviewed by experts skilled in secure coding and web application security. While this review is less intensive than a full manual code audit, it is essential to ensure that developers are not distracted by false alarms, allowing them to focus on actual development work.
Dynamic testing
Dynamic application security testing (DAST) is an entirely different animal than SAST. Where SAST is called white box testing because of the tester has the same view as the developer, dynamic testing is called black box testing because the tester has the view of the cyber attacker. This means two things: 1) the web application is in its running state; and 2) there is typically little to no detail of the inner workings of the web application available to the tester (it is possible to glean details of the web app via various nefarious practices, but that is beyond the scope of this discussion).
These distinctions between static and dynamic testing are important. If a tester finds a flaw with a web application in its running state, it is typically much easier to verify than with static testing. The tester simply has to run through the same steps again to make sure the flaw appears again. Essentially, the false positive rate is lower (especially when using automated tools) in dynamic testing than with static testing. So, let’s look at some of the methods of dynamically testing web applications.
Similar to the manual effort involved in the static code review mentioned above, dynamic testing can be performed using a manual methodology by an individual. This involves someone with expertise in web application security running through the application page by page looking for potential flaws in web forms, authentication mechanisms, session management, and others. This type of testing, while more accurate, can be time-consuming and expensive. Modern development timelines may cause this level of testing to become untenable to an organization.
Again, in a similar fashion as static testing, automated dynamic web application analyzers were created to cut down the time needed for a full dynamic test of an app. Typically, the analyzer is setup and ran by an individual (who does not need to be as proficient in dynamic testing) to perform and automated analysis of the website structure (called “spidering”) to find all the potential vulnerable elements of the web app. These are recorded and tested according to the configuration of the analyzer, and the results are provided when testing is completed (these results also need to be reviewed by an expert).
Outsourcing SAST & DAST
SAST and DAST testing demand specialized expertise that many organizations lack the resources or desire to build in-house. As a result, outsourcing becomes a critical solution. A variety of companies offer application testing services, each with its own approach. Some focus on intensive manual efforts, such as code review and dynamic testing, often within niche firms or specialized divisions of larger organizations. Others combine manual and automated testing for a more balanced approach, while some rely almost exclusively on automation to streamline assessments. Regardless of the method, the expertise required for effective testing is indispensable.
A recent and powerful development in the world of dynamic testing is the rise of bug bounty programs. These programs harness the power of crowdsourcing to identify software vulnerabilities, with a particular focus on security flaws. Participants sign up as testers and conduct dynamic testing on web applications. If they uncover a unique and valid flaw, they are rewarded — often with a monetary prize. Some companies even outsource the management of these programs to specialized firms. While controversial, bug bounties offer the distinct advantage of leveraging a diverse group of testers with varied techniques, leading to more comprehensive security assessments.
The approach your company adopts for testing web applications depends on your business goals and available resources. However, regardless of the strategy, it’s strongly recommended to integrate both static and dynamic testing into your security program. Each method has its strengths and weaknesses, but when used together, they create a more robust and effective security testing strategy for your web applications.
