Overview

OpenBSD is a security-focused, free Unix-like operating system forked from NetBSD in 1995 by Theo de Raadt. The project’s hallmarks are proactive security auditing, correctness, and integrated cryptography. OpenBSD developers perform rigorous, continuous code review, resulting in an operating system that has had only two remote holes in the default install in over two decades.

Key Features

• PF Firewall: Packet Filter (PF) is a stateful firewall originally developed for OpenBSD and now used in Apple macOS and other systems
• Proactive Security: Entire base system is continuously audited for security bugs; features like W^X, ASLR, and stack protector are default
• OpenSSH & LibreSSL: Created and maintained by the OpenBSD project; OpenSSH is the most widely used SSH implementation globally
• Correctness over Speed: Prioritises clean, auditable, and correct code over performance, integrated with thorough documentation and man pages

Platforms

x86-64, ARMv7/ARMv8, PowerPC, RISC-V, SPARC64 and others

Licence

BSD, ISC, other permissive licenses

Website

openbsd.org