OpenBSD

OpenBSD is a free, open-source Unix-like operating system derived from BSD. It was initiated by Theo de Raadt in 1995 as a fork of NetBSD and released as a distinct project in 1996. The project aims to produce a secure, correct, and openly auditable operating system, with a reputation for careful code review and conservative feature growth.

Security and reliability are central to OpenBSD’s design. The project emphasizes secure-by-default configurations, extensive code auditing, and rigorous memory protection. Notable technologies include the pf packet filter firewall, strong memory protection with W^X, and privilege-restriction mechanisms such as pledge and unveil. OpenBSD also ships with LibreSSL, a fork of OpenSSL developed to improve cryptographic code quality, and a suite of hardened base utilities and services. OpenSSH, a widely used secure remote login tool, is included in the base system.

OpenBSD uses its own base system and a large Ports collection for third-party software. Binary packages can be installed and managed with tools such as pkg_add. The system employs a simple rc-based init framework and emphasizes portability across multiple architectures.

The project maintains regular releases and issues security advisories for vulnerabilities. OpenBSD is used on servers, network appliances, and embedded devices where security and reliability are prioritized. It is often regarded as a reference platform for secure system design and review, reflecting a development model centered on transparency, auditable code, and cautious feature inclusion.