Wondering what DAST is and how it can help in identifying vulnerabilities? Well, you have landed on the right page. This article discusses DAST scanning, how it works, and common vulnerabilities it can identify. So, let's dive in!

What is DAST?

DAST stands for Dynamic Application Security Testing. It is a comprehensive testing mechanism that simulates real-world attack scenarios to identify security vulnerabilities and attacks in a running (dynamic) web application.

DAST scanning can be performed from an unauthenticated or authenticated user perspective. DAST scanning offers several benefits to development and security teams, i.e. frequent and faster testing that saves time and money by identifying vulnerabilities earlier in the lifecycle. When DAST scanning is included as part of the Continuous Integration/Continuous Development (CI/CD) pipeline, it is referred to as “Secure DevOps” or “DevSecOps.”

This testing identifies security flaws in web applications and APIs that could be exploited by attackers. Some popular dynamic application security testing tools are OWASP ZAP, Netsparker, Burp Suite, Acunetix, etc. Here is a complete list of OWASP Vulnerability Scanning tools.

How Does DAST Work?

Let’s dive into how DAST scanning works.

Target Identification: This is the first step of the DAST scan process. In this, the DAST scanner needs to understand what it will test. This step involves specifying the URL of web apps or API endpoints, tech stack and the excluded URLs. This may include testing with no credentials (black box) or with credentials (gray box).

Crawling: The second step involves crawling the target application. DAST scanner traverses the application’s web pages and functionalities, mapping the sitemap and the URLs with various inputs and endpoints for the next step.

Attack Simulation: Once crawling is completed, the tool uses the sitemap collected from the previous step and simulates the attack scenarios using its built-in attack database. It inputs malicious data with attack payloads into URL parameters, cookies, and HTTP headers to test and examine how the application responds to the malformed payloads.

Some common yet powerful techniques that DAST utilises are fuzzing (injecting abrupt data) and parameter tampering (changing user inputs).

Analysis of Responses: In this step, the tool analyses the application's response to identify the vulnerabilities. If the app returns error messages, behaves abruptly, or discloses sensitive information, the tool flags report them as vulnerabilities. This phase may produce false positives.

Reporting: Once the analysis is completed, the tool generates detailed reports about the vulnerabilities identified, the severity of each vulnerability, remediation suggestions, and other related information. The DAST scanning may take up to 24 hours to complete and generate the report, depending on the target application's size and complexity.

Re-testing: After vulnerabilities are remediated, the tool can be re-run to validate that the security issues have been addressed correctly. Some scanners offer automated vulnerability retest capability, such as Blacklock, which can be a very handy tool for development teams.

Common Vulnerabilities Identified by DAST

Now that we have understood what DAST is and how it works, let's go through some of the common vulnerabilities identified by DAST.

Security Misconfigurations

Generally known as “low-hanging vulnerabilities”, which is a common issue in web applications. DAST tools are good at picking such issues:

● Default credentials: Detecting when apps still make use of default, common and weak credentials.

● Excessive open ports and services: Identifying services running on the server end that shouldn’t be exposed or misconfigured.

● Out-of-date software versions: Identifying when apps or their components are running older or outdated versions of software.

● Directory traversals: Listing the contents of the web server to identify the sensitive data.

Injection Flaws

Injection flaws arise when unauthorized data is provided to an interpreter as part of a command or query. The most common types are:

● SQL injection: Manipulating database queries to access, change, or delete data without authorization.

● Command Injection: Executing arbitrary system commands on the host OS.

Cross-Site Scripting [XSS]

Cross-Site Scripting vulnerabilities, also known as XSS, allow attackers to insert malicious scripts into web pages that are executed on another user browser. DAST tools can identify and detect all three types of XSS:

● Reflected XSS: This is when the attacker’s injected scripts are immediately executed on the user browsers without sanitization, output encoding and input validation.

● Stored XSS: Where malicious scripts are stored on the database and then executed on the user's browser when another user visits the affected field or page.

● Document Object Model [DOM]-based XSS: This is where vulnerabilities occur on client-side scripts that manipulate the client-side DOM.

Sensitive Data Exposure

Another use case of the DAST tool is to identify and report sensitive data exposure, such as:

● API key disclosure: Detects sensitive data that may be hardcoded or stored in client-side JavaScript files.

● Verbose error messages: Identify and detect when the application throws stack trace error messages disclosing server paths, backend source code and file paths.

● Unencrypted data transmission: DAST can detect when sensitive information is sent over insecure protocols.

Apart from these, such tools can also help identify inadequate data masking, if any. It detects when applications fail to properly mask sensitive data in outputs or logs, highlighting areas where sensitive information may be at risk.

The Bottom Lines

In today's rapidly evolving cybersecurity landscape, organizations and enterprises must priorities the security practices of their web applications. Adopting DAST tools is one of the best modern security testing strategies that offers benefits in terms of:

● Continuous security testing

● Early detection of vulnerabilities

● Comprehensive coverage

● Saves time and money

● Meets compliance requirements

● Sift-left approach to your security journey

However, there are various challenges in its implementation, such as high false positive rates, high cost, skillset requirements, limited visibility, and testing requirements. Despite these challenges, the perks of DAST in identifying critical vulnerabilities early in the lifecycle help improve the overall security posture of the web application, making it an essential component of any comprehensive security and development program.

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