m0n0wall is an embedded firewall distribution of FreeBSD, one of the BSDoperating system descendants. It provides a small image which can be put on Compact Flash cards as well as on CD-ROMs 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.
On February 15, 2015 it was announced the "m0n0wall project has officially ended. No development will be done anymore, and there will be no further releases". The pfSense project, which forked from the m0n0wall project in 2004 is still actively maintained. However, the founder Manuel Kasper recommends OPNsense, which forked from pfSense in February 2015 as an alternative.