A free penetration testing and vulnerability discovery toolkit entirely written in python.

ReadyARM appliance which provides the ability to monitor computer networks for unauthorized intruders and scan for vulnerabilities.

A web server scanner which performs tests against web servers for multiple items, including over 2200 potentially dangerous files/CGIs, versions on over 140 servers, and problems on over 210 servers.

Developers of NMAP, a network port scanner and service detector offering stealth SYN scan, ping sweep, FTP bounce, UDP scan and operating system fingerprinting. Downloads, documentation, security tools directory and a mailing lists archive. [Windows, ...

Internet Scanner Tool. Performs scheduled and selective probes of communication services, operating systems, applications and routers to uncover and report systems vulnerabilities that might be open to attack.

IPsonar maps and provides risk assessment to network assets.

Security scanner for Linux, BSD, Solaris, and other flavors of Unix. Performs over 900 remote security checks, and suggests solutions for security problems.

It includes network/host scanner, a set of additional features currently limited to whois and traceroute and numerous options to fully customize the scan process.

A vulnerability assessment and compliance solution that scans applications, databases, networks, and operating systems.

Web server fingerprinting and enumeration.