DAST, short for “dynamic application security testing,” is the process of analyzing the frontend of a web application using attack simulations to uncover vulnerabilities. In it, security testers evaluate the application from the outside by attacking it like threat actors would.
Security testers typically use a DAST scanner for testing. The scanner looks for results that are not part of the expected result set to identify vulnerabilities.
So, what is DAST comparable to? You can compare the scanner to security guards who ensure all the doors and windows in the building are locked so no intruders can enter. They also stand guard at night or when none of the tenants are in.
Other interesting terms…
Read More about DAST
DAST is just one of the many checks security teams perform to assess the effectiveness of an organization’s defenses. Learn more about it here.
How Does DAST Work?
The process essentially takes a black box approach in that it emulates the actions of threat actors when they try to breach a web application.
Step 1: Scanning
The first step is to use a DAST scanner to simulate user interactions with a running web application. It sends various HyperText Transport Protocol (HTTP) requests to do that. This phase identifies all the pages, links, functions, and entry points the application accesses or uses.
Step 2: Analysis
While the requests are being sent, the scanner analyzes the application’s responses to spot anomalies, error messages, and unexpected behaviors that indicate vulnerabilities. All the potential vulnerabilities’ locations and actions are recorded for future reference. They could prove useful in manual testing, if necessary.
Step 3: Attack Simulation
The scanner then imitates SQL injection, XSS, and cross-site request forgery (CSRF) attacks. It thus locates security vulnerabilities like misconfigurations, data exposure, and authentication issues that threat actors can exploit.
Step 4: Reporting
After the attack simulation and analysis, the scanner produces reports outlining the vulnerabilities identified, including their severity and potential attack scenarios. These reports can guide developers and security teams in the future. Note that DAST only identifies security issues but leaves remediation to development teams.
Step 5: Addressing False Positives
Sometimes, DAST tools can yield false positives. They can mistakenly flag something as a vulnerability. As such, human validation and prioritization may be required.
What Types of Vulnerabilities Does DAST Detect?
DAST very effectively detects vulnerabilities that may affect a web application’s security. And DAST scanners can identify several vulnerabilities that we named below.
SQL Injection
A SQL injection attack lets threat actors exploit a web application vulnerability by interfering with the queries the application makes to its database. As such, attackers can view data they are not authorized to. This data can include user information or any other data the application has access to. In many cases, threat actors modify or delete this data, causing persistent changes to the application’s content or behavior.
In some situations, attackers escalate a SQL injection attack to compromise the web application’s server or other backend infrastructure. Sometimes, they can also launch a denial-of-service (DoS) attack.
Cross-Site Scripting
An XSS attack lets threat actors compromise user interactions with vulnerable web applications. To do that, attackers bypass the same origin policy that is designed to segregate different websites.
In this attack, threat actors masquerade as normal users, carrying out actions they perform to access their data. This is especially dangerous if the users being mimicked have privileged access, which gives attackers full control over all of the application’s functionality and data.
Cross-Site Request Forgery
A CSRF attack forces users to execute unwanted actions on running web applications while they are logged in. It requires a little help from social engineering to trick users into executing actions. Normal users can be manipulated to transfer funds, change their email address, and others. Things get worse if the victims have administrative access since attackers can compromise entire web applications.
Unvalidated Redirects
DAST is also effective in identifying unvalidated redirects that purposely mislead users to unsafe websites, exposing them to phishing or malware infection.
Business Logic Flaws
Sometimes, users encounter web application issues that developers did not see in their code. DAST can spot these flaws as well so they will not lead to undesirable actions or vulnerabilities.
What Are the Types of DAST Tools?
DAST solutions can be categorized based on cost and features. Here is a comparison.
| Types Based on Cost | Types Based on Features |
| Commercial Scanners – Web assessment tools companies need to purchase | Legacy Tools – Often lack automation features and typically focus on basic testing—sending requests, receiving responses, and making preliminary assessments – Do not offer full vulnerability validation as they only list potential security issues |
| Open-Source Scanners – Free tools | Modern Tools – Can be automated and offer a more thorough review of web application vulnerabilities – Can seamlessly integrate into the software development life cycle (SDLC) and operate in the background – Come with automation servers and present scan results as tickets in developers’ issue trackers – May provide proof of exploitation, eliminating the time needed for manual verification by penetration testers or security experts |
Who Are the Typical DAST Users?
The process is very useful for developers, security professionals, DevOps teams, managed service providers (MSPs), large enterprises, and application programming interface (API)-first teams.
API-First Teams
Teams building applications with APIs rely on the process to test their security, ensuring they are protected against common vulnerabilities.
Developers
Developers rely on the process to identify vulnerabilities in their code as they are being developed and tested. This lets them fix issues early on in the SDLC. This shift-left approach to security testing is common in modern development practices.
DevOps Teams
DevOps teams typically integrate DAST tools into continuous integration and continuous development (CI/CD) pipelines to automate security testing and ensure new code changes do not introduce vulnerabilities. This integration streamlines the development process and helps them release secure applications faster.
Large Enterprises
Large enterprises secure their web applications and APIs, especially those with complex architectures and high security requirements, using the process.
Managed Service Providers
MSPs use the process to provide security testing services to clients, ensuring the applications they manage are protected against vulnerabilities.
Security Professionals
Security teams rely on the process to assess the security posture of applications, identify potential attack vectors, and verify the effectiveness of security controls. They often combine DAST with other security testing methods like static application security testing (SAST).
What Are the Uses of DAST?
Here is a list of DAST use cases.
End-to-End Life Cycle Testing
When combined with major CI/CD tools, it is ideal for full life cycle testing.
Scheduled Testing
Automation allows for scheduled scans, including one-time or recurring tests.
Web Application Protection
Companies in need of a proactive means to protect web applications via automated scanning can benefit from DAST.
What Benefits Does DAST Provide?
DAST is considered critical to web application security testing. Its benefits include:
- Automation: DAST solutions can easily be integrated into DevOps and CI/CD pipelines. As such, developers can run automated security testing as early as possible in the development process, significantly reducing remediation costs.
- Comprehensive vulnerability discovery: The process can uncover many vulnerabilities that can lead to misconfigurations and SQL injection and XSS attacks, among others.
- Fewer false positives: The process usually yields fewer false positives and negatives when simulating user actions than other methods like SAST.
- Industry standards alignment: Companies often use DAST to adhere to industry standards and aid in regulatory reporting. Those that use the OWASP Top 10 list as a compliance benchmark for application security risks can benefit from it most.
- Language agnosticism: Since the process works from the outside in, it does not depend on the programming language the application uses. It also works with different frameworks. In addition, DAST effectively tests both web interfaces and APIs that attackers exploit most.
- Realistic and repeatable testing: Since the process emulates real-world attacker behavior, it is a practical solution for identifying vulnerabilities that threat actors can exploit. It is also repeatable, making ongoing vulnerability assessment possible even as applications evolve.
- Versatility: The process can be deployed at various stages of the SDLC since it tests running web applications and those that have already been deployed without modifications. As such, it is also useful in evaluating legacy systems.
What Challenges Can DAST Users Face?
While DAST can greatly improve the security of web applications, it also comes with its own set of challenges and limitations. Take a look at some of them below.
Irregular Results
Using DAST tools requires proper configuration to simulate attacks effectively, depending on the web application’s context. They should be configured to properly handle authentication and manage sessions. Without regular tuning, they can produce false positives and negatives. Their scanning parameters should thus be aligned in terms of timeout limits, request throttling, and authentication configurations based on the application’s requirements and environment.
When used, the scan results also need to be reviewed so vulnerability filters can be refined to reduce false positives. This way, users can minimize noise and optimize the analysis process to only focus on genuine threats.
Limited Visibility
Even if DAST significantly improves security testing, solutions can provide an overstated picture of security. In some instances, they may struggle to fully assess applications, especially those with complex authentication mechanisms, leaving vulnerabilities undetected. As such, regular penetration testing that can uncover deeper, context-specific threats should complement DAST. Using both offers better protection against threats.
Performance Issues
Since DAST thoroughly tests for all potential vulnerabilities, comprehensive scans can be time-consuming. This can delay pipeline execution and extend deployment schedules. Misconfigured scan settings can also overwhelm resources, leading to potential downtime in the environments where testing is happening.
To solve this issue, optimize scan configurations. Perform incremental or targeted instead of full scans during the development cycle.
How Does DAST Differ from SAST?
DAST is often compared with SAST. Which of the two is better for companies’ use? Consider what both processes do by looking at their features below.
| DAST | SAST |
| Focuses on runtime behavior, examining the application when its full functionality is active | Analyzes source code to identify vulnerabilities (e.g., outdated libraries, insecure code, or hardcoded credentials) |
| Analyzes an application from the outside in | Looks at the application from the inside out |
| Simulates attacks launched by threat actors | |
| Looks for unexpected scan results to identify security vulnerabilities | |
| Detects issues that SAST may have missed (e.g., authentication bypasses, weak passwords, and vulnerabilities in components that only surface when the application runs) |
As you have seen, DAST and SAST do not perform the same functions. Instead, they complement each other so it is advisable to use both to ensure the security of your web applications.
Key Takeaways
- DAST (Dynamic Application Security Testing) analyzes running web applications from the outside in using real attack simulations.
- It follows a structured process: scanning, analysis, attack simulation, reporting, and false-positive validation.
- DAST identifies runtime vulnerabilities such as SQL injection, XSS, CSRF, unvalidated redirects, and business logic flaws.
- Tools range from open-source to commercial, and from legacy to modern solutions, allowing flexibility by budget and feature needs.
- It supports lifecycle security through scheduled testing and ongoing web application protection.
- Key benefits include automation and broad vulnerability discovery, often with fewer false positives than SAST. Challenges include limited code visibility and potential performance impact.
- DAST complements SAST: DAST tests applications in runtime, while SAST analyzes source code. Using both provides stronger overall security coverage.
Sources
- https://en.wikipedia.org/wiki/Dynamic_application_security_testing
- https://www.ibm.com/think/topics/dynamic-application-security-testing
- https://www.fortinet.com/products/dynamic-application-security-testing
- https://github.com/resources/articles/security/what-is-dast
