What is Dynamic Application Security Testing (DAST)?

With cyber threats growing in sophistication and frequency, organizations must implement comprehensive security testing strategies to protect their applications and sensitive data. One of the most effective approaches to improving security posture and identifying security vulnerabilities in running applications is Dynamic Application Security Testing (DAST).

DAST represents a crucial component of modern application security programs, offering unique insights that complement other testing methodologies. Unlike testing approaches that examine code in isolation, DAST evaluates applications in their natural runtime environment, simulating real-world attack scenarios that malicious actors might employ. This testing method has gained significant traction among enterprise security teams, software engineering organizations, and penetration testers due to its practical approach and reliable results.

What is DAST?

Dynamic Application Security Testing, also known as DAST, is a form of testing a running version of your application to identify potential security vulnerabilities. With DAST, a scanner sends requests to your web application that simulate malicious attackers and evaluates the response received from the application for an indication of a security bug. As they run through the test suite of simulated attacks, any potential vulnerabilities are recorded for review.

DAST tools have long been a favorite of enterprise security teams, software engineering teams, and penetration testers alike. This form of testing finds vulnerabilities that your team has introduced in the software development lifecycle, as well as exploitable vulnerabilities from open-source components used within the application. It is often used alongside Static Application Security Testing (SAST) and Software Composition Analysis (SCA) tools. DAST is known for its low false positive rates and clear surfacing of application security risks.

DAST scanners find a wide variety of web application security vulnerabilities without looking directly at an application’s source code. This can include SQL Injection, Cross-Site Scripting (XSS), Cross-Site Request Forgery (CSRF), and many other vulnerabilities. These scanners find the majority of the OWASP Top 10 vulnerabilities.

How does DAST work?

DAST scanners initiate their process by targeting the host where your application is deployed. This could be a publicly accessible website or web application; however, it is generally recommended to perform DAST scans in a pre-production environment. Since the scanner emulates an attacker, it could potentially modify or delete data in your production environment, leading to undesirable consequences.

Once the scanner targets the host, it launches an HTML spider to catalog all accessible paths and actions. Depending on the chosen tool, it might also employ an Ajax spider for single-page applications, utilize the OpenAPI specification to test your REST APIs, or examine the GraphQL introspection endpoint to map out your GraphQL API query tree. Ideally, your tooling should comprehensively cover your application and associated APIs and automate this process as much as possible.

Then, the scanner executes a suite of tests, transmitting requests to all identified paths/endpoints and analyzing the responses for indications of security vulnerabilities. The results are then compiled in the report or displayed via the interface of your DAST tool, ideally providing the essential information developers require to remediate any discovered issues.

Why is DAST important?

Dynamic application security testing is an excellent way to ensure that you are delivering secure software applications and avoiding the risk of a breach. DAST offers developers a major security advantage by helping to identify security vulnerabilities and generating high-quality vulnerability assessment reports.

DAST is essential for organizations that need to assess applications in their runtime environment, where vulnerabilities that only manifest during execution can be discovered. This includes runtime vulnerabilities such as SQL injection, cross-site scripting (XSS), and other input-related attacks that may not be apparent through static code analysis alone.

The application security testing landscape has shifted over the past decades, with APIs serving as a primary potential attack vector. DAST provides critical testing capabilities for modern applications that rely heavily on APIs and complex interactions between different components.

DAST vs. Other Security Testing Types

Application security testing encompasses several methodologies, each offering unique advantages and focusing on different aspects of security assessment. Understanding these different approaches helps teams choose the right combination of tools to optimize their security testing strategy.

Static Application Security Testing (SAST) analyzes an application’s source code, binaries, or bytecode before the application is executed. It examines the code structure, logic, and patterns for security vulnerabilities, making it ideal for early detection. By finding issues like insecure coding practices or logic flaws, SAST can identify vulnerabilities like buffer overflows, hardcoded secrets, and syntax errors, all without the need for a running application. However, a challenge with SAST tools is a higher likelihood of false positives, which can lead to time-consuming triage for developers and security staff alike.

Interactive Application Security Testing (IAST) combines elements of both SAST and DAST by instrumenting applications with sensors that monitor application behavior during testing. IAST provides real-time vulnerability detection by analyzing code execution, data flow, and application behavior from within the running application. This approach offers detailed visibility into how vulnerabilities can be exploited while providing precise location information for remediation.

Software Composition Analysis (SCA) focuses on identifying security vulnerabilities in third-party and open-source components used within applications. SCA tools scan dependency manifests, container images, and compiled binaries to identify known vulnerabilities in external libraries and frameworks. As modern applications rely heavily on open-source components, SCA has become essential for managing supply chain security risks.

Runtime Application Self-Protection (RASP) takes a different approach by embedding security directly into applications to provide real-time protection against attacks. Unlike traditional testing methods, RASP monitors application behavior in production and can block malicious requests automatically, serving as both a detection and prevention mechanism.

Here’s how these testing approaches compare:

Aspect	DAST	SAST	IAST	SCA	RASP
Testing Phase	Runtime/Staging	Development	Runtime with instrumentation	Development/Build	Production
Code Access Required	No	Yes	Yes	Partial (dependencies)	Yes
Testing Approach	Black box	White box	Gray box	Component analysis	Real-time monitoring
False Positive Rate	Low	High	Medium	Low	Low
Vulnerability Types	Runtime flaws, injection attacks	Code-level issues, logic flaws	Comprehensive coverage	Known CVEs in dependencies	Real-time attacks
Performance Impact	None on production	None	Medium	None	Low to medium
Integration Timing	CI/CD, scheduled	IDE, build process	Testing phase	Build/CI pipeline	Production deployment
Coverage Scope	Accessible application surfaces	Full codebase	Executed code paths	Third-party components	Application runtime

DAST focuses on testing a running application from an external perspective, simulating attacks without access to source code. This makes DAST solutions ideal for detecting vulnerabilities that only manifest in runtime environments, such as SQL injection, cross-site scripting (XSS), and other input-related attacks. Because it interacts with the application in its final environment by simulating user interactions, DAST provides real-world results with fewer false positives.

In a comprehensive security strategy, these testing methods should be used together rather than in isolation. SAST catches vulnerabilities early in development, IAST provides detailed runtime analysis during testing, SCA ensures third-party components are secure, DAST confirms that the application is secure in its deployed state, and RASP provides ongoing protection in production. This layered approach ensures comprehensive security coverage throughout the development lifecycle.

Benefits of DAST

DAST provides numerous advantages that make it an essential component of application security programs. The primary benefit is its ability to test applications in realistic conditions, providing security teams with actionable intelligence about actual security risks rather than theoretical possibilities.

DAST is known for its low false positive rates and clear surfacing of application security risks. Because DAST tests running applications and evaluates actual responses, it typically generates fewer false alarms compared to static analysis tools. This characteristic reduces the time and resources required for vulnerability triage.

DAST’s vendor-agnostic approach works effectively regardless of the programming languages, frameworks, or technologies used to build the application. This flexibility makes DAST particularly valuable for organizations with diverse technology stacks or those that need to assess third-party applications.

The automation capabilities of modern DAST tools provide substantial operational benefits. The future of application security is automated and integrated with the DevOps pipeline (known as DevSecOps by many). With automated security scans in the CI/CD pipeline, there are many benefits that lead to faster discovery and fixes of security threats, including developers being alerted of any new vulnerabilities before they hit production, optionally breaking the build to ensure a review happens before the release.

Limitations and Challenges of DAST

While DAST offers significant advantages, it does have certain limitations that organizations must consider when implementing their security testing strategies.

DAST may miss vulnerabilities in non-executable code or code paths that are not accessible through the application’s user interface or API endpoints. If certain functionality requires specific conditions to execute, DAST may not be able to test these areas effectively.

The timing of DAST implementation can present challenges since it requires a running application, typically occurring later in the development process when applications are deployed to testing or staging environments. This timing means that vulnerabilities discovered through DAST may require more significant remediation efforts compared to issues identified earlier in the development cycle.

Authentication and session management can complicate DAST implementation. If your application requires user login, you will need a scanner that supports authenticated testing methods or scans. You should ensure that the vendor accommodates your form of authenticated scanning, such as cookie-based, external token, and bearer token.

Single Page Applications (SPAs), built-in frameworks like React or Angular, have rapidly grown in popularity in recent years. Without a static DOM, traditional HTML spiders cannot identify the various paths against which to run a dynamic application security test. Testing SPAs necessitates using a tool equipped with an AJAX spider, alongside a tool capable of scanning the underlying APIs.

Best Practices for Effective DAST

Implementing DAST effectively requires careful planning and adherence to established best practices to maximize the value while minimizing potential risks and operational challenges.

Scan Frequency: Consider how often you would like to kick off scans. CI/CD automated scans provide the best results, with developers alerted of any new vulnerabilities before they hit production. Testing can be run against underlying services and APIs instead of the customer-facing application, leading to faster identification of the underlying issue when a bug is found.

Application Target: As highlighted earlier, scanning in a pre-production environment rather than in a production setting offers numerous advantages. These include the ability to detect vulnerabilities before they become live, avoiding the need to bypass rate limiters, firewalls, and Web Application Firewalls (WAFs), and reducing the time required for fixes.

User of Tool: When selecting a tool, one of the primary considerations should be the individual who will use the tool. Developer-centric security tooling is growing in popularity, with tools increasingly being used with a focus on enabling developers to write more secure code, make triage decisions, and deploy fixes in their existing workflows.

API Security Testing: If you are running application security testing against modern applications, ensure that the tooling you select supports API testing as a first-class part of the tool. Additionally, if you are using GraphQL as part of your tech stack, you’ll want to ensure that GraphQL API testing is supported by your DAST tool.

Popular DAST Tools

There are many DAST tools in the market, including several open-source or free options. Below is a list of the leading tools in the space that you could use for testing.

StackHawk

StackHawk is a modern DAST tool built for automation in CI/CD. For teams that want to catch vulnerabilities before they hit production and integrate security testing into engineering workflows, StackHawk is the leading option. StackHawk is built on top of the open-source ZAP project and provides engineering teams with simplified automation, vulnerability triage, and fixes of security findings.

ZAP

ZAP is an open-source DAST scanner that stands as the most widely used application security scanner in the industry. Having set the standard for the past decade, ZAP excels in automation. It offers both a desktop application for scanning and an API that enables automated scanning of web applications.

Burp Suite

Burp Suite, a product of PortSwigger, is a penetration testing tool. Burp Suite is an excellent tool for penetration testers or in-house application security teams looking to do manual scans. There is also an enterprise edition that leverages agent deployments.

Detectify

Detectify is a more modern entrant in the DAST space, although it leverages a crowdsourcing approach to identifying vulnerabilities. The DAST scanner runs against production applications on a schedule.

Netsparker

Netsparker is an established DAST tool that supports enterprise security teams. With on-premise deployment and a professional services arm to lead rollout, Netsparker fits enterprises that are not yet investing in DevSecOps.

Rapid7

InsightAppSec is the DAST solution provided by Rapid7, another long-standing enterprise security platform. InsightAppSec supports on-premise deployment and scheduled scans of production, making it another excellent solution for enterprises that are not yet investing in DevSecOps.

Veracode

Veracode is an enterprise application security platform with solutions including SAST, SCA, IAST, and now DAST solutions. For large enterprises that prioritize a single platform for all application security needs, Veracode may be the right choice. However, if you’re looking for Veracode alternatives that better suit modern software security teams, there are several strong options to consider.

Conclusion

Dynamic application security testing is an excellent way to ensure that you are delivering secure software applications and avoiding the risk of a breach. Getting started is relatively simple, and there are numerous free and open-source tools to support your testing process and enhance your existing security posture. DAST offers developers a major security advantage by helping to identify security vulnerabilities and generating high-quality vulnerability assessment reports.

Once you decide to get started with dynamic application security testing, consider the deployment model that works best for your organization, whether you need authenticated scanning capabilities, and how the tool will integrate with your existing development workflows. Most development teams will prefer a SaaS solution, but some companies still require an on-premise solution.

The key message here is to simply begin testing! Whether beginning with open-source tools or implementing enterprise solutions, the security benefits of DAST become apparent quickly. For organizations looking for the fastest way to get started with DAST, StackHawk provides a modern platform built by developers to help developers find security vulnerabilities more efficiently.