Frox is a transparent ftp proxy which is released under the GPL. It optionally supports caching (either through an external http cache (eg. squid), or by maintaining a cache locally), and/or running a virus scanner, on downloaded files. It is written with security in mind, and in the default setup it runs as a non root user in a chroot jail.

http://frox.sf.net

-- LucaGibelli - 11 Feb 2007