A power cycle is the process of fully turning a device off and then back on again, long enough for volatile memory and running state to clear. Unlike a simple software restart, a true power cycle removes electrical power from the hardware, which can reset stuck processes, release hung drivers, and return embedded devices to a known starting point.
In cyber security, power cycling matters because many security controls depend on stable state. It is a common recovery step for routers, cameras, smart devices, and other appliances that stop responding after a crash, bad update, or firmware bug. Defenders also use it to test whether a problem is transient or persistent; if an issue disappears after a power cycle, it may point to instability rather than compromise. Attackers can exploit this behavior too, for example by forcing reboots to disrupt monitoring or to make a device forget temporary state. For that reason, repeated need for power cycles is often a sign that the device’s firmware, configuration, or trust boundaries need review.