Nmap ("Network Mapper") is a free and open source (license) utility for network exploration or security auditing. Many systems and network administrators also find it useful for tasks such as network inventory, managing service upgrade schedules, and monitoring host or service uptime.
Gpg4win is a installer package for Windows (2000/XP/2003/Vista) with computer programs and handbooks for EMail and file encryption. Both relevant cryptography standards are supported, OpenPGP and S/MIME (the latter is in progress and currently works with GnuPG2 and Claws Mail). Gpg4win and the software included with Gpg4win are Free Software.