An open source operating system is a system software platform whose source code is publicly available for anyone to inspect, modify, and redistribute. Examples include desktop, server, and embedded platforms built by communities or vendors that publish the code under open licenses. Because the code is open, security teams can audit how authentication, networking, permissions, and update mechanisms work instead of relying only on vendor claims.
In cyber security, this transparency is both a strength and a responsibility. Defenders can review code for backdoors, misconfigurations, and vulnerable components, while attackers can also study the same code to find weak defaults or unpatched flaws. Open source operating systems are common in hardening, container hosting, and network appliances because they can be customized and monitored closely. Their security depends less on secrecy and more on timely patching, trustworthy builds, and careful configuration.