A system restart is a forced reboot that interrupts normal use after a serious fault, crash, or watchdog failure. Unlike a planned reboot, it happens because the operating system, a driver, or hardware can no longer keep the machine running safely.
In cyber security, sudden restarts matter because they can signal anything from an unstable low-level driver to a kernel crash triggered by malformed input or exploitation attempts. Attackers may also force reboots as a denial-of-service tactic, breaking availability and sometimes erasing useful evidence in memory. For defenders, repeated unexpected restarts are a strong clue that logs, crash dumps, and recent updates should be reviewed together. In practice, reboot patterns often help separate a simple compatibility problem from a deeper security or reliability issue.