OS-level isolation is the set of operating system controls that keep processes, files, devices, and execution environments separated from one another. It can be implemented with user permissions, namespaces, containers, virtual machines, app sandboxes, and platform features such as restricted file access or blocked network paths. The goal is to let code run while reducing what it can reach if it misbehaves.
In cyber security, OS-level isolation is a core defense against sandbox escapes and lateral movement. If an attacker breaks out of a restricted runtime, the next barrier should be the host OS boundary, not just application rules. Strong isolation can limit credential theft, file tampering, and command execution on the local machine. Defenders use it to contain untrusted code, AI agents, plugins, and malware; attackers try to bypass it to turn a limited foothold into full system access.