Dynamic Application Security Testing
DAST (Dynamic Application Security Testing) is a "black-box" testing approach that examines an application in its running state to identify security vulnerabilities. Unlike other methodologies, DAST interacts with the application from an external perspective, simulating real-world attacks without having knowledge of the source code or internal architecture.
This technique is fundamental for discovering flaws that only manifest when the application is running, such as server configuration errors, session management problems and business logic vulnerabilities.
How Does DAST Work?​
DAST tools operate by sending a series of malicious or unexpected requests to the application and analyzing the responses for anomalies that indicate a vulnerability. The process generally follows these steps:
- Crawling: The tool maps the application to understand its structure, identifying pages, forms, parameters and other data entry points.
- Attack Simulation: Based on the mapping, the tool launches a variety of automated attacks aimed at exploiting known vulnerabilities, such as SQL Injection, Cross-Site Scripting (XSS), Cross-Site Request Forgery (CSRF) and authentication failures.
- Response Analysis: The tool monitors the application's responses to these attacks. Unexpected responses, detailed error messages or abnormal behaviors may indicate the presence of a vulnerability.
- Reports: At the end of the process, a detailed report is generated with the vulnerabilities found, their severity and, in many cases, recommendations for correction.
Advantages and Disadvantages​
| Advantages | Disadvantages |
|---|---|
| Simulates Real Attacks: Offers a realistic perspective on how an external attacker would try to compromise the application. | Does Not Identify the Flaw Location: Without access to the code, it can be difficult for developers to locate the exact line of vulnerable code. |
| Low False Positive Rate: Since vulnerabilities are actively exploited, confirmation of their existence is more accurate. | Limited Code Coverage: May not test all parts of the application, especially if certain functionalities are not discovered during scanning. |
| Language and Framework Independence: Being "black-box", it can be used on any application, regardless of development technology. | Requires a Running Environment: The application needs to be functional and running for the test to be performed. |
| Detects Configuration Problems: It is effective for finding environment and server configuration errors, which SAST cannot see. | Can Be Slow: Scanning and executing multiple attack vectors on a complex application can take considerable time. |
DAST in the Development Lifecycle (SDLC)​
Traditionally, DAST is applied in the final phases of the cycle, such as testing, staging or production environments. However, with the adoption of DevSecOps practices, there is a strong movement to "shift left", integrating DAST scanners earlier and in an automated way into CI/CD pipelines to identify flaws more quickly.
It is important to emphasize that DAST is not a single solution. For a robust security strategy, it is recommended to combine it with SAST (source code analysis) and SCA (open source dependency analysis).
DAST Solutions and Tools​
The market offers a wide range of solutions. The ideal choice depends on factors such as budget, DevSecOps process maturity, application type and team profile.
"All-in-One" Platforms (AppSec Platforms)​
These platforms integrate SAST, DAST, SCA and other technologies into a single solution. The advantage is centralized management and data correlation, although the individual DAST tool may not be as specialized as a dedicated solution.
- Checkmarx One: Considered one of the most complete platforms, its great advantage is tracking a vulnerability discovered by DAST to the exact line of code pointed out by SAST.
- Snyk Developer Security Platform: Unifies SAST, SCA and IaC. Added DAST after acquiring Probely, with strong focus on API and modern application security.
- GitLab Ultimate: For teams already using GitLab, the Ultimate version integrates DAST, SAST and SCA directly into the CI/CD pipeline, offering unbeatable convenience.
- Other Notable Platforms: Veracode Application Security Platform, Synopsys Polaris Platform, Rapid7 Application Security.
Dedicated DAST Tools (Commercial)​
These tools specialize in DAST and often offer the deepest and most accurate analysis.
- Invicti (formerly Netsparker): Famous for Proof-Based Scanning technology, which automatically confirms vulnerabilities, almost completely eliminating false positives. Ideal for: Companies that need large-scale automation and high precision.
- Acunetix: Stands out for speed and excellent ability to scan complex applications (SPAs). Ideal for: Small and medium-sized businesses (SMBs) that need a fast and effective tool.
- PortSwigger Burp Suite Professional: The industry standard for pentesting, its automated scanner is extremely powerful and flexible. Ideal for: Security professionals and teams that combine automated testing with in-depth manual analysis.
Open Source DAST Tools​
- OWASP ZAP (Zed Attack Proxy): Is the most popular and complete open source DAST tool on the planet. Highly configurable, with an active community and an add-on marketplace. Ideal for: Absolutely anyone — from students to large corporations looking for a powerful and free DAST solution to integrate into pipelines.
- Nikto: A fast and straightforward scanner, focused on finding vulnerabilities, dangerous files and misconfigurations on web servers. Ideal for: System administrators for quick audits on server configuration.