M0n0wall

m0n0wall is an embedded firewall distribution of FreeBSD, one of the BSD operating system descendants. It provides a small image which can be put on Compact Flash cards as well as on CDROMs and hard disks. It runs on a number of embedded platforms and generic PCs. The PC version can be run with just a Live CD and a floppy disk to store configuration data, or on a single Compact Flash card (with an IDE adapter). This eliminates the need for a hard drive, which reduces noise and heat levels.