OpenBSD Operating System

OpenBSD is a free and open-source Unix-like operating system emphasizing security, correctness, and proactive cryptography, forked from NetBSD in 1995 by Theo de Raadt. Known for producing some of the most security-focused software in the world, OpenBSD has pioneered numerous security innovations adopted industry-wide. Key features include: proactive security (secure by default philosophy with only essential services enabled, extensive code auditing, and removal of unsafe constructs), OpenSSH (the ubiquitous SSH protocol implementation created by the OpenBSD team, used on virtually every Unix system worldwide), pledge and unveil (kernel-level system call restriction and filesystem path visibility controls for privilege reduction), ASLR and W^X (address space layout randomization and write XOR execute memory protection enabled by default), stack protector (stack cookies, ASLR, and position-independent executables for all base system binaries), ports and packages (curated third-party software collection with source-based ports tree and binary package repository), packet filter pf (stateful firewall with altq traffic shaping, anchors for hierarchical rules, and spamd greylisting), crypto framework (hardware crypto acceleration, IPsec, and IKED IKEv2 daemon), relayd (layer 7 load balancer and TLS terminator), CARP (Common Address Reduction Protocol for failover), and cross-platform support for amd64, arm64, i386, macppc, sparc64, and more.