Dynamic Application Security Testing (DAST) is a type of security testing that is used to identify and assess vulnerabilities in web applications while they are running. It is also known as black-box testing, as it does not require access to the source code of the application. DAST works by simulating attacks on the web application, similar to how a hacker would attempt to exploit vulnerabilities. It uses automated tools to scan the application and identify potential security flaws such as SQL injection, cross-site scripting, and insecure authentication. These tools also have the ability to crawl through the application and identify all the entry points that can be used for an attack.