Burp Suite is a Java-based tool for testing the security of web applications. It has free and paid versions. The tool's modules include Target, Proxy, Spider, Scanner, Intruder, Repeater, Sequencer, Decoder, Comparer, and Extender. The Target module provides an overview of the application. The Proxy module intercepts and inspects traffic between the browser and server. The Spider module automatically crawls the application. The Scanner module automatically scans for vulnerabilities. The Intruder module automates customized attacks. The Repeater module manually manipulates and reissues requests.