Dynamic Application Security Testing (DAST): A Complete Guide

According to research by Statista, over 353 million individuals were impacted by data breaches and leaks in 2023 alone. Many of these breaches stem from vulnerabilities within software applications. What's even trickier is that some vulnerabilities, like misconfigurations and security policy violations, only become apparent when the software is up and running.

Dynamic application security testing (DAST) helps detect potential security vulnerabilities in software by mimicking how hackers might exploit weaknesses.

Understanding how DAST works can help you build and release secure software products faster. Here's everything you need to know.

What is DAST?

DAST is a type of application security testing that detects security vulnerabilities by simulating attacks against an application in its running/operating state. This black-box testing method examines the application from the “outside-in” by attacking it like a malicious user would. According to our State of Software Quality 2024 report, 45% of the software developers we surveyed are currently employing dynamic application security testing tools. 

Using DAST during the software development lifecycle enables teams to uncover vulnerabilities before their applications are in production. DAST is completely language agnostic and can be automated in a continuous integration/continuous deployment (CI/CD) pipeline, automated on a schedule, or run independently by using on-demand DAST scans.

DAST tools simulate how a user interacts with an application and generate reports on a wide range of security issues. How the application responds to these simulations helps determine whether it is vulnerable to a real-life, malicious attack.

Why Is DAST Important?

DAST helps identify vulnerabilities that might be missed by other testing methods, such as Static Application Security Testing (SAST), which analyzes code but doesn't involve running the application. DAST tools test applications in real-world scenarios, making it possible to find configuration and authentication problems or other runtime vulnerabilities that may impact your application’s functionality and security. It’s also a good method for preventing regressions and doesn’t depend on a specific programming language. As long as the application can be accessed through a browser, a DAST tool can typically scan it for vulnerabilities.

By proactively identifying and remediating vulnerabilities in running code, DAST tools can help organizations reduce the risk of data breaches, malware infections, and other security incidents.

DAST can also help you comply with standards or get certifications, like HIPAA or PCI DSS.

How Does DAST Work?

DAST tools work by actively interacting with a web application while it is running. The testing process typically involves the following steps:

1. Target identification: The DAST tool first scans the application's structure, including its pages, directories, and visible entry points. It then automatically navigates through the application, much like a search engine spider, to map out a comprehensive view of all accessible areas.
   
   
2. Vulnerability detection: Based on the identified structure, the DAST tool prepares a series of test attacks that simulate common security threats. The prepared tests are executed against the application, incorporating a range of inputs and user behaviors to probe for weaknesses.
   
   
3. Analysis of responses: The DAST tool monitors the application's responses to the simulated attacks, analyzing the outputs and behaviors for signs of vulnerability. It also scrutinizes the application's behavior, such as error codes, unintended outputs, or changes in state that could indicate a security issue.
   
   
4. Reporting: Once the analysis is complete, DAST tools generate detailed reports. These reports outline each discovered vulnerability and its severity level, and sometimes even offer suggestions for how to fix it.
   
   
5. Re-testing: After fixes are implemented, the DAST tool can be rerun to confirm that the vulnerabilities have been successfully addressed.

Pros and Cons of DAST

DAST tools are great for analyzing running applications. However, they cannot identify vulnerabilities in the source code. As with every technology, DAST has its pros and cons. Let’s take a close look at them.

Pros of DAST

• Low risk of reporting false positives: DAST identifies vulnerabilities on a running application by exploiting them. As such, it allows you to verify if a potential vulnerability is real and if it poses a threat to your application.
  
  
• Detection of runtime issues: DAST tools interact with a running application, enabling it to detect both compile-time and runtime issues.
  
  
• Works with every programming language: DAST is the only security testing method that isn’t programming language specific since it doesn’t look at source code. As such, if your application is implemented with a niche programming language, DAST may be your only choice.
  
  
• Uses regression testing: DAST makes it easy to check a previous vulnerability. If a vulnerability is reproduced, it can be added to the DAST test suit. As such, every subsequent release will include the same interactions that previously led to the issues.

Cons of DAST

• Doesn’t show problematic code locations: Since DAST doesn’t analyze code, it’s impossible to correlate the vulnerabilities and the exact line of code where they happened.
  
  
• Slower testing process: The requirements to execute and use a DAST tool can slow the testing process, even when using automated testing methods.
  
  
• Fixing vulnerabilities is more expensive: Since DAST needs a deployed application, it can only be performed later in the development lifecycle, increasing the cost required to fix the identified vulnerabilities.
  
  
• Doesn’t have complete code coverage: DAST tools analyze a running application, meaning they might miss vulnerabilities in parts of the code that are not executed.
  
  
• Manual testing may be needed: Sometimes, it’s impossible to automate your application’s execution and usage, so you’ll still have to test the application manually for every release.

DAST Best Practices

If your team wants to achieve optimum website security, then understanding some DAST best practices and how to implement them is pivotal. Here are some best practices to follow during DAST tests.

Integrate DAST Early in the SDLC

Traditionally, DAST tools were introduced toward the end of the software development lifecycle, typically during the testing or production phase. However, integrating DAST in the code development phase allows software teams to identify vulnerabilities as soon as possible and fix them while development is ongoing.

This approach is part of the "Shift Left" movement in DevSecOps, where security is incorporated earlier in the development process rather than being an afterthought. Security concerns are not treated as a final-stage concern but rather as an ongoing part of the development workflow. 

Integrating DAST early also sets the foundation for continuous testing/continuous deployment (CI/CD). Organizations can set up DAST to run every time code is pushed to the local repository, ensuring new changes don’t introduce vulnerabilities. 

Implement Comprehensive Test Coverage

Software development has become more complex than ever, with a growing variety of open-source frameworks, third-party APIs, libraries, cloud services, architectural designs, and viewing devices. While this offers endless possibilities, it also introduces more potential attack vectors for cybercriminals.

A DAST tool helps you mitigate security risks by thoroughly examining all accessible parts of a running application (e.g., form inputs, APIs, and third-party code) to identify potential security vulnerabilities. During testing, ensure that you cover all parts of your application, such as:

• Front-end Web Applications: These are the traditional user-facing part of web applications. DAST can simulate attacks on web pages, forms, and other interactive elements to find vulnerabilities like XSS or insecure direct object references.
  
  
• Backend and APIs: APIs are often a primary attack surface for modern applications, especially with the rise of microservices and cloud-native architectures. APIs can expose sensitive data; if not properly secured, they’re vulnerable to attacks like SQL injection, DDoS, or improper authorization.
  
  
• Third-party libraries: Though software composition analysis (SCA) is tailor-made for spotting problematic third-party code and dependencies, DAST can also help identify abnormal behavior in third-party components during runtime.

Make DAST a part of your CI/CD pipeline, so tests are automatically triggered with every code change. This minimizes the risk of security flaws making it to production.

Prioritize High-Risk Areas

Certain parts of an application are more susceptible to attacks due to their role in handling sensitive operations or data. During testing, these areas should be prioritized to avoid devastating security breaches. 

Here are some of the key areas to focus on:

Authentication: Authentication is an essential part of any dynamic application. A compromised authentication system can allow attackers to impersonate users or gain unauthorized access to sensitive information. For example, weaknesses in password policies, brute force protection, multi-factor authentication (MFA), or session management can all lead to compromised accounts. Your DAST tools should test for these authentication-related vulnerabilities.

Authorization: Proper authorization systems must be in place to prevent privilege escalation (a situation in which attackers exploit system design flaws to access sensitive information or perform unauthorized actions). Use a DAST tool to verify that the right authorization mechanisms are in place.

Sensitive Data Handling: Applications that handle sensitive information such as Personally Identifiable Information (PII), payment details, or medical records need to be tested rigorously for vulnerabilities that could expose this data. Your DAST tests should assess whether sensitive data is transmitted and stored securely. Check for issues such as improper encryption, weak cryptography algorithms, insecure data storage, and data leakage through error messages or logs.

Third-party dependencies: Modern applications often rely on third-party libraries, components, APIs, or services to function. While these integrations can provide powerful features and accelerate development, they can also introduce security risks if not properly vetted. Many of these third-party components may contain known vulnerabilities, lack proper security patches, or expose insecure configurations that attackers could exploit. 

Customize Scan Configurations

For optimal results, it's essential to tailor your DAST scans to align with your system's architecture and configuration. Most DAST tools offer detailed customization options that enable you to fine-tune your security scans for maximum effectiveness.

Here are some configurations to consider:

HTTP Basic and Form-Based Authentication: Configure your DAST tool to look for default or weak keys and check if the application properly enforces HTTPS. If your web application has a login form, configure your DAST to simulate login attempts with common attack techniques like brute force, SQL injection, cross-site scripting (XSS), and session fixation. Most tools provide a dashboard area where you can configure your credentials.

Scheduled Scans: When scheduling automatic DAST scans, choose times when infrastructure usage is low to minimize operational disruption. This could mean scheduling scans to run at midnight or during the weekend when user activity is at its lowest. 

Integrations: Most DAST tools offer integrations for popular CI/CD platforms, cloud platforms, vulnerability management tools, and notification/ticketing systems, enabling you to automate the application security testing process within your development pipeline. For instance, by integrating with CI/CD platforms like Jenkins, GitLab, or Azure DevOps, you can trigger scans automatically with each code change or deployment.  

Reporting & Analytics: Create customized dashboards to view key security findings relevant to your project. These dashboards can display insights such as the frequency and severity of vulnerabilities found, trends over time, and the status of ongoing remediation efforts. You can tailor the visualizations to focus on specific areas, like high-risk vulnerabilities, frequently recurring issues, or the effectiveness of security measures applied during the development cycle.

Manage False Positives and Negatives

One of the most common challenges with DAST tools is the occurrence of false positives (flagging safe actions as malicious) and false negatives (missing actual vulnerabilities). 

Here are some steps you can take to manage this problem:

• Integrate a vulnerability management solution to keep track of issues you mark as false positives. These tools store historical results, so you typically only have to check a false positive once, and any duplicates or similar results are flagged automatically.
  
  
• Simplify the scanning process to minimize complexity, as overly complex scans often increase the amount of false positives. Configuring your tool to prioritize the most critical vulnerabilities will reduce unnecessary noise and give more accurate results.
  
  
• Continuously monitor and adjust your security measures. Regularly review security alerts to differentiate between real threats and false positives. Finally, stay updated on the latest vulnerabilities and adjust your security measures accordingly.

Monitor for Performance Impacts

Running DAST scans can put a strain on system resources because these tools simulate real-world attack scenarios, often sending a high volume of requests or testing large numbers of endpoints. If these scans are not properly managed, they can slow down application performance, overwhelm servers, or even cause temporary downtime. 

Some tips:

• Schedule scans carefully and avoid running them during peak business hours or other critical periods (for example, you can schedule scans to run at night or during weekends.)
  
  
• Some DAST tools allow you to configure the intensity or scope of the scan. This might include limiting the number of concurrent requests or throttling certain attack simulations. 
  
  
• Use incremental scans, i.e., test smaller portions of the application at a time, rather than attempting to scan everything in one go. This can spread out the load on the system, ensuring that performance is not drastically impacted during testing.
  
  
• Employ staging or pre-production environments during testing, as they are typically isolated from production systems, meaning that any negative performance impacts or errors caused by security testing won’t affect actual users. 
  
  
• Keep an eye on real-time metrics like CPU utilization, memory consumption, disk I/O, and network throughput during scans. By tracking these metrics, you can quickly identify if the DAST scan is consuming excessive resources, allowing you to adjust the scan's intensity or pause it if necessary.

Use Complementary Testing Methods

DAST only covers a portion of the security landscape, focusing on vulnerabilities found in running applications. To build a more comprehensive security strategy, complement DAST with Static Application Security Testing (SAST), Interactive Application Security Testing (IAST), penetrative testing, IaC Security, and runtime security monitoring.

Common DAST Challenges and How to Overcome Them

Although DAST is a powerful and necessary application security testing practice, organizations often face challenges during its implementation. Here are some common obstacles organizations face and how to overcome them.

Choosing the Right DAST Tool

The first step in implementing DAST is selecting the right tool. With so many options available, choosing the best one can be challenging, as not all tools are suited to every situation.  

Two major things to consider when selecting a DAST tool are its coverage level and accuracy. You want a tool that can scan all of your application’s components with great accuracy and a low occurrence of false positives/negatives. 

Along with coverage and accuracy, evaluate the tool's speed and scalability to ensure fast, efficient scans, especially for large and complex applications. Verify that it integrates seamlessly with your development tools and processes, and is easy to use.

Unreliable Reporting 

When you start using a DAST tool, it’s normal to encounter false positives or negatives. But if the problem persists after fine-tuning your configurations to match your application’s needs, you need to consider other solutions.

While false positives can be reduced with manual review, false negatives may require supplementary security testing methods (e.g., penetration testing or SAST) to identify overlooked vulnerabilities. Teams can also incorporate a vulnerability management tool to keep track of issues marked as false positives.

Complex Authentication Mechanisms

DAST tools can have difficulty scanning applications that require multi-factor authentication (MFA), CAPTCHA, or other complex login procedures, as these measures can block automated scanners from accessing the application. As a result, the tool may fail to complete scans or miss vulnerabilities behind these authentication barriers. 

To overcome this, provide your tool with the necessary credentials or tokens for authenticated scans, and configure them to navigate through advanced authentication steps. 

Handling Dynamic Content and Behavior

Web technologies like JavaScript, AJAX, and web sockets add interactivity and dynamic behavior to websites, but they also create avenues for cybercriminals to attack your application. 

While DAST is the best security measure to combat these threats, some DAST tools might struggle to handle the extreme dynamism and multifacetedness of many modern applications. 

Here are some steps you can take:

• Integrate DAST scans directly into the CI/CD pipeline, ensuring they run after every change to catch vulnerabilities before production.
  
  
• Use a crawler or proxy to capture and analyze dynamic requests and responses between the client and server, as well as generate relevant test.
   
• Employ a browser or headless browser to execute and render dynamic content, simulate user actions, and interact with the application. For more comprehensive scanning, tools that support multiple protocols and formats (such as REST, SOAP, JSON, and XML) can parse and validate these dynamic elements effectively.

Testing Distributed Systems

Modern applications, especially those built using microservices, APIs, or serverless architectures, present significant challenges in testing due to their distributed nature. These applications often span across multiple services, systems, and platforms, each potentially running in different environments or even cloud providers. This complexity makes traditional testing approaches, which often focus on monolithic or tightly coupled systems, less effective.

Choose DAST tools capable of testing across all components, from APIs to microservices. Consider integrating DAST with other security tools to provide more comprehensive vulnerability coverage.

5 Key Considerations for Choosing DAST Tools

With a variety of DAST tool options available, it is crucial to consider key factors to ensure that the tool you select aligns with your security and business needs. 

1. Vulnerability Detection

Evaluate the DAST tool's ability to detect a wide range of vulnerabilities. It should cover the OWASP Top 10 at a minimum and be capable of identifying both common and advanced threats. 

2. Comprehensive Coverage

Most organizations have multiple websites and applications, each containing multiple points of attack. Ensuring security across the board is paramount, as overlooking one area can leave others exposed. Ensure that the DAST tool can comprehensively cover your entire application and its dependencies. This includes not only the main application but also third-party libraries, APIs, and other components that could introduce vulnerabilities. A thorough assessment helps identify and mitigate potential security risks across the entire application stack.

3. Integration and Automation

To maximize efficiency, your DAST tool should integrate smoothly with your existing development workflow. Ideally, it should connect with your CI/CD pipeline, enabling automated scans as part of the development process. This way, vulnerabilities are identified and addressed early on, preventing them from reaching production.

4. Scalability and Performance

As your application grows in complexity and user base, your DAST tool should scale accordingly. The tool should efficiently handle increased testing demands without compromising performance. Look for a solution that offers flexible deployment options, such as on-premise, cloud, or hybrid, to accommodate your specific infrastructure needs.

5. Automated Compliance Reporting

If your organization needs to comply with regulatory standards or industry-specific requirements, choose a DAST tool that offers automated compliance reporting. The tool should generate reports for standards such as PCI DSS, HIPAA, GDPR, and ISO/IEC 27001, highlighting compliance status, vulnerabilities, and remediation actions. Automated reporting not only saves time but also ensures that you meet regulatory obligations and maintain a strong security posture.

DAST vs. SAST: How They Complement Each Other

DAST and SAST are fundamental components of software security, each offering unique advantages that complement each other when used together.

Scope of Testing

SAST is a white-box testing method that focuses on analyzing the source code and identifying potential vulnerabilities without executing the code. It scans the codebase, looking for issues such as SQL injection, memory leaks, and other known security vulnerabilities.

DAST, on the other hand, tests the application in a live environment by actively interacting with it during runtime. It simulates real-world attacks to uncover vulnerabilities that may only surface when the application is running, such as authentication weaknesses, input validation errors, and runtime configuration issues.

Timing in the Development Cycle

SAST is typically performed early in the development process, often during the coding phase or during code reviews. It helps identify and fix security issues at an early stage, reducing the likelihood of vulnerabilities making their way into the final product.

DAST is usually conducted later in the development cycle, after the application is deployed or in a staging environment that closely resembles the production environment. It helps validate the security of the running application and detects vulnerabilities that may have been missed during static analysis.

Automation and Integration

Both DAST and SAST can be automated and integrated into the software development lifecycle (SDLC) and CI/CD pipelines. This enables organizations to conduct regular security testing and identify vulnerabilities before software release, reducing the overall risk of security breaches.

Organizations can achieve a comprehensive security assessment of their applications by combining DAST and SAST, along with other security testing techniques such as dependency scanning, license analysis, and penetration testing. This multi-layered approach helps identify and mitigate a wide range of security threats, enhancing the application's overall security posture.

Use SAST and DAST for Comprehensive Security 

While DAST offers a powerful shield against real-world attacks, it's important to remember that true application security is a layered defense. The most effective approach combines the strengths of both DAST and SAST.

Automating DAST and SAST scans with CI/CD allows you to accelerate development time without sacrificing your application’s security.

We understand the value of a holistic security strategy, which is why we offer a range of security solutions designed to address all the critical aspects of application security. 

Ready to take your application security to the next level?