ClosedBSD is a derivative of FreeBSD aimed at providing firewall (networking) and NAT services. ClosedBSD also aims for a small footprint in terms of size, available as a floppy disk image at 1.4MB and as a CD-ROM ISO at 12.8MB. In spite of its small size, the software includes a fully-functional Ncurses-based interface.

One of the advantages of ClosedBSD is that it can be run directly off a floppy disk or a CD-ROM, with no hard drive required. It can also be run on relatively old hardware; the diskette version requires a x86-based computer with 8MB of Random Access Memory, while the CD-ROM version requires 32MB of RAM.

ClosedBSD is released under the terms of the BSD License.

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