A safety interlock is a control that blocks a machine from operating unless a required protective condition is true. That condition might be a closed cover, a locked door, a set pressure range, a valid sensor reading, or an armed emergency-stop circuit. Interlocks are designed to fail safe: if a switch, cable, or controller is missing or ambiguous, the system should stop rather than run.
In cyber security, interlocks matter because many attacks target the logic that decides whether a system is allowed to act. In industrial control systems, medical devices, and lab equipment, an attacker who disables, spoofs, or overrides interlock signals can turn a guarded process into a hazardous one. Defenders therefore treat interlocks as part of a safety boundary, using tamper-resistant wiring, independent hardware checks, and strong authentication for any remote control path. In practice, a well-designed interlock limits damage even when software fails or an operator makes a mistake.