Tenable Nessus is a world-leader in active vulnerability scanners. It features high-speed discovery, configuration auditing, asset profiling, sensitive data discovery, and vulnerability analysis of your security posture. Nessus scanners may be distributed throughout an entire enterprise, inside DMZs, and across physically separate networks. It is free of charge for personal use in a non-enterprise environment.
Racket (formerly PLT Scheme) is a programming language suitable for implementation tasks ranging from scripting to application development, including GUIs, Web services, etc. It includes the DrRacket programming environment, a virtual machine with a just-in-time compiler, tools for creating stand-alone executables, the Racket Web server, extensive libraries, documentation for both beginners and experts, and more. It supports the creation of new programming languages through a rich, expressive syntax system. Example languages include Typed Racket, ACL2, FrTime, and Lazy Racket.