OpenBSD
OpenBSD is a free operating system made by volunteers, with security as its top goal. An operating system is the base software that runs a computer or server.
OpenBSD is one operating system. An operating system is the base software that starts first when a computer turns on and connects programs to the machine, like the foundation and pipes of a building. OpenBSD is made by volunteers and is free to use, and its official site says the aim is to be number one in the industry for security. It is known for checking every critical part file by file and for switching off non-essential services by default.
For example Anthropic says its AI found a 27-year-old weakness in this system that let someone crash a machine remotely, and that it has been patched. Even a system known for security had a flaw, so keep your website server updated without delay.
Source: OpenBSD · OpenBSD Security · OpenBSD Project Goals · Claude Mythos Preview's cybersecurity capabilities · Project Glasswing: Securing critical software for the AI era (checked 2026-10-26)