OpenBSD is a secure, freely available, multi-platform 4.4BSD-based Unix-like operating system. OpenBSD, led by Theo de Raadt, was originally derived from the NetBSD project, and thus it shares much of NetBSD's history and portability. The split was due to philosophical (and developer personality) differences. OpenBSD's hallmark is the priority given by its developers to careful and proactive auditing of system's code, which in turn contributes to the stability and security of OpenBSD.
Until June 2002 the OpenBSD web-page featured the slogan "No remote hole in the default install, in nearly 6 years". This was changed to "Only one remote hole in the default install, in more than 7 years" after an exploit was discovered in OpenSSH. Some have criticized this statement since not much is enabled in the default install of OpenBSD, and stable releases have included software that later were found to have remote holes. Others counter that one of the OpenBSD project's fundamental innovations is the drive for systems to be "Secure by Default". It is standard, and indeed fundamental, security practice to enable as few services as possible on production machines. Be that as it may, OpenBSD is still a remarkably secure and stable operating system.