OpenBSD is a Unix-like computer operating system descended from Berkeley Software Distribution (BSD), a Research Unix derivative developed at the University of California, Berkeley. It was forked from NetBSD by project leader Theo de Raadt in late 1995. As well as the operating system, the OpenBSD Project has produced portable versions of numerous subsystems, most notably PF, OpenSSH and OpenNTPD, which are very widely available as packages in other operating systems.