OpenVAS is an open source remote security vulnerability scanner, designed to search for networked devices and computers, discover accessible ports and services, and to test for vulnerabilities on any such ports; plugins allow for further expansion.
Nikto is an Open Source (GPL) web server scanner which performs comprehensive tests against web servers for multiple items, including over 3500 potentially dangerous files/CGIs, versions on over 900 servers, and version specific problems on over 250 servers. Scan items and plugins are frequently
... [More] updated and can be automatically updated (if desired). [Less]