Dynamic Application Security Testing: Why, How, Pros and Cons

What Is Dynamic Application Security Testing (DAST)?

Dynamic Application Security Testing (DAST) has become a critical component of web application security. DAST is a process that involves the testing of applications from the outside - by examining them in their running state during a simulation of an attack. It's an automated method that identifies security vulnerabilities, without the need for access to the source code, and is compatible with all programming languages or frameworks.

DAST tools use a black-box testing approach, where the tester doesn't have any knowledge of the system's architecture or internal workings. The primary focus is on exposing potential vulnerabilities that may exist in the running web application, which might be exploited in a real-world attack scenario. Through this process, DAST can identify common security loopholes such as cross-site scripting (XSS), SQL injection, and security misconfigurations.

Unlike other security testing methods, DAST doesn't require access to the source code. This means that it can be implemented late in the development life cycle, making it an effective tool for identifying vulnerabilities in applications that are already running in testing environments or deployed to production. DAST can provide a detailed understanding of vulnerabilities, offering actionable guidance that can guide the development team in remediating them.

This is part of a series of articles about Application Security Testing

Why Is DAST Important? 

With the increasing number of web applications being developed and deployed, the potential attack surface for cybercriminals is also expanding. DAST plays a crucial role in securing these applications, safeguarding sensitive data, and ensuring the smooth operation of digital services.

DAST helps organizations identify vulnerabilities that could be exploited by attackers. By testing the application in its running state, DAST can detect security loopholes that static testing methods may miss. These vulnerabilities can then be rectified before they are exploited, reducing the risk of data breaches and system downtime.

Lastly, DAST provides a cost-effective solution for maintaining application security. By automating the testing process, and simulating thousands of possible attack patterns, DAST reduces the need for manual testing, saving time and resources, and can prevent costly security incidents.

How Does DAST Work? 

Dynamic application security testing operates by simulating cyber-attacks on a web application in its operational environment. The process starts with DAST tools crawling the application to understand its structure and functionality. This phase involves mapping out the application and identifying potential entry points for attacks. The DAST tool then sends various malicious inputs to these entry points, mimicking the tactics used by cybercriminals.

As the simulated attacks are carried out, the DAST tool monitors the application's responses. If the application reacts unexpectedly, such as returning sensitive information or crashing, this indicates a potential vulnerability. The DAST tool then generates a report detailing these vulnerabilities, providing information on their location, potential impact, and suggested remediation steps.

DAST Tools vs. SAST Tools 

DAST and SAST (Static Application Security Testing) are two common methods used in application security testing, each with its unique focus and capabilities.

SAST tools analyze the source code of an application without executing it. This method is often referred to as white-box testing because it requires access to the internal structure and design of the application. SAST is effective in identifying vulnerabilities early in the software development life cycle (SDLC), such as code quality issues, insecure coding practices, and other potential security weaknesses. This early detection is beneficial as it allows developers to address security concerns during the coding phase, reducing the cost and complexity of fixes later in the cycle.

DAST, in contrast, tests applications in their running state. This is a black-box approach that does not require access to the source code. DAST tools can simulate external attacks on applications, identify runtime issues, and are particularly valuable for testing the parts of an application that interact with external systems, such as APIs and user interfaces.

Many organizations integrate SAST and DAST to gain a holistic view of an application's security posture. SAST’s early detection of vulnerabilities in the code complements DAST’s ability to identify runtime issues that only appear during the application’s operation. This combined approach makes it possible to address both inherent code vulnerabilities and operational security gaps.

Learn more in our detailed guide to DAST vs SAST

DAST Advantages 

Detecting Runtime Issues

Since DAST tests the application in its running state, it can identify vulnerabilities that only appear when the application is operational. These can include issues like session management problems, access control issues, and insecure server configurations.

By identifying these runtime issues, DAST gives developers a clearer understanding of how their applications behave in a live environment. This allows them to rectify issues that might not be apparent during the development stage.

Low False Positive Rates

False positives, where a tool incorrectly identifies a vulnerability, can be a significant drain on resources as developers and security teams spend time investigating non-existent issues. Because DAST tests the application in its running state and examines the application's responses to simulated attacks, it's less likely to generate false positives compared to static testing methods.

This reduction in false positives saves time and resources, allowing developers to focus on genuine vulnerabilities, and providing a more accurate reflection of the application's security posture.

Related content: Read our guide to dast tools

Language Agnostic

DAST is language agnostic. This means that it's capable of testing web applications regardless of the programming language they're written in. This is a significant advantage, given that modern applications are often built with a mix of different languages and frameworks. 

The language-agnostic nature of DAST makes it applicable to complex microservices applications and also ensures that teams can use the same DAST tool to scan their entire application portfolio.

Outsider's Perspective Testing

DAST's ability to test from an external viewpoint simulates an outsider attempting to exploit vulnerabilities, offering insights not visible from internal testing methods.

Real-World Attack Simulation

DAST effectively mimics real-world attack scenarios, testing the application's responses to various threats, and providing a practical evaluation of security preparedness.

Third-Party Component Analysis 

DAST's capability to identify vulnerabilities in third-party components and services integrated within applications is vital for a comprehensive security strategy.

DAST Limitations

Contextual API Security Analysis

DAST, while effective in general vulnerability detection, often lacks the depth to understand an API's specific business logic and context. This limitation arises because DAST primarily interacts with APIs at a surface level, analyzing responses to simulated attacks. It doesn't delve into the underlying logic or comprehend the nuanced ways APIs are intended to function within a particular business context. Consequently, DAST may overlook complex business logic vulnerabilities that don't manifest in straightforward operational scenarios but could pose significant risks in real-world applications.

Late Appearance in SDLC

One of the significant limitations of DAST is that it usually appears late in the software development life cycle (SDLC). This can lead to delays in the development process because it takes more time to fix vulnerabilities at later stages. The later you find a security weakness, the more expensive it becomes to fix. If a vulnerability is discovered early in the development cycle, developers can address it more easily, leading to considerable cost savings.

Vulnerability Location

DAST can struggle to pinpoint the exact location of vulnerabilities within the code. DAST is excellent at identifying that a vulnerability exists but can come up short when trying to locate the exact line of code responsible. As a result, developers may need to spend extra time locating the problem, which can slow down the development process.

Code Coverage

Code coverage refers to the percentage of code that is reviewed during a testing process. DAST does not have access to the underlying source code, so it cannot review the entire application. For example, modules that are not executed at runtime or are not directly connected to the user interface might be invisible to DAST tools.

Developer Disconnect: Security Focus vs. Developer Workflow

Another limitation of traditional DAST is its orientation toward security owners rather than developers. This approach can create a disconnect, as DAST typically presents findings in a security-centric language, which might not align with the everyday workflow and understanding of developers. This can lead to challenges in communication and collaboration between security teams and developers, potentially hindering the efficient resolution of identified vulnerabilities.

Performance Impact

DAST, due to its exhaustive and fuzz testing nature, often consumes significant time and processing resources. This can be a drawback in agile development settings where rapid testing and feedback are crucial. The extensive and fuzz-driven nature of DAST's testing can slow down the overall development process, especially in continuous integration environments.

Complex Configuration 

Implementing DAST involves a steep learning curve and substantial configuration effort. This complexity can be a barrier, particularly for teams without extensive security expertise. The onboarding process requires careful tuning of the tool to fit specific application contexts, which can be time-consuming and resource-intensive.

Integration Challenges

Integrating DAST tools into existing development workflows and CI/CD pipelines can present difficulties. These tools often require additional adjustments to work seamlessly with the development process, potentially disrupting established workflows. The lack of easy integration can hinder the tool's adoption, especially in environments where quick and efficient deployment is essential.

Learn more in our detailed guide to dast tools

How Next-Generation API Security Testing Tools Overcome DAST Limitations

Pynt offers a unique approach to API security testing, addressing both the advantages and limitations of DAST.

• Runtime Issue Detection: Pynt, like DAST, excels at detecting runtime issues in APIs. By testing APIs in their operational state, Pynt identifies vulnerabilities that may only appear during live usage.
• Low False Positives: Pynt's testing methodology, similar to DAST, reduces false positives. It provides accurate results, helping developers focus on real vulnerabilities rather than spending time on false alarms.
• Language Agnostic: Pynt shares DAST's language-agnostic nature. It can effectively test APIs regardless of the programming languages used, making it suitable for complex microservices applications with diverse tech stacks.
• Testing from an Outsider's Perspective: Pynt, like DAST, tests APIs from an external perspective, simulating real-world attack scenarios. This perspective helps uncover vulnerabilities that might not be visible from within the development environment.
• Third-party Component Testing: Pynt, similar to DAST, effectively identifies issues in third-party components and services integrated within the application. It ensures a comprehensive security assessment.
• Contextual API Security Analysis: Pynt goes beyond DAST by providing contextual API security analysis. While DAST may overlook complex business logic vulnerabilities, Pynt understands the nuanced ways APIs function within specific business contexts by analyzing the traffic of the existing functional tests, reducing the risk of missing critical issues.
• Early Integration in SDLC: Pynt's unique approach allows for early integration into the software development life cycle (SDLC). Unlike DAST, which often appears late, Pynt's proactive testing can identify vulnerabilities at an earlier stage, resulting in cost savings.
• Comprehensive Coverage: Although Pynt doesn't access the source code, it assesses code from a holistic perspective. It identifies vulnerabilities by analyzing response payloads, ensuring comprehensive code coverage, while providing contextual evidence for the vulnerability's existence.
• Integration with Development Tools: Pynt integrates seamlessly with existing development and CI/CD tools, facilitating its adoption within development workflows.

Learn more about Pynt API Security Testing

Best Practices for DAST Implementation

Use DAST as Early in the SDLC as Possible

The earlier you identify a vulnerability, the cheaper and easier it is to fix. Therefore, DAST should be used as early in the SDLC as possible. Run DAST scans as soon as applications are deployed to a testing or staging environment, to discover runtime issues early. 

In addition, next-generation DAST tools can integrate with developer tools to conduct scans even during early development stages. This allows vulnerabilities to be fixed during development, rather than after the application has been deployed.

Integrate DAST with Your CI/CD Pipeline

Continuous Integration/Continuous Deployment (CI/CD) is a key part of modern software development practices. It involves the integration of code changes and deployment of the application in an automated and continuous manner. DAST should be integrated into the CI/CD pipeline to ensure continuous security testing.

By integrating DAST into the CI/CD pipeline, security testing becomes part of the regular development process. This ensures that every change to the code is tested for security vulnerabilities. It also makes the process of identifying and fixing vulnerabilities more efficient, as it happens in real time.

Adopt Defensive Coding Practices

Designing and coding with security in mind is a crucial part of DAST implementation. Developers should be trained in defensive coding practices. This involves writing code in such a way that its functionality is not compromised by security vulnerabilities.

Defensive coding practices include input validation, output encoding, and proper error handling among others. These practices help prevent common vulnerabilities like XSS and SQL injection. Developers can thus reduce the number of vulnerabilities that DAST identifies, and developers then need to remediate.

Use tools that leverage DAST for Continuous API Security

Tools that leverage DAST advantages and deal with its drawbacks more are equipped to provide continuous security for APIs, monitoring them for vulnerabilities in real-time. This is crucial since APIs are continuously updated and can develop new vulnerabilities over time.

The integration of DAST into continuous integration and continuous deployment (CI/CD) pipelines allows for the automated testing of APIs with each update or new release. This continuous testing ensures that any newly introduced or previously undetected vulnerabilities are quickly identified and addressed.

Moreover, by automatically discovering API endpoints and regularly scanning them using such tools, organizations can discover API vulnerabilities as soon as they occur and remediate them, preventing damaging security breaches.

Learn more about API security

Pynt vs traditional DAST

Overall, Pynt leverages the advantages of DAST while overcoming its limitations, providing a robust API security testing solution that aligns with modern development practices.

Pynt offers a holistic approach to API security, ensuring that vulnerabilities are identified early, false positives are minimized, and complex business logic scenarios are thoroughly assessed.

Learn more about Pynt

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