A defrost cycle is a programmed pause in cooling equipment that warms coils long enough to melt ice buildup. Refrigeration controllers trigger it on a schedule or in response to conditions such as frost accumulation, and then return the system to normal cooling.
In cyber security, the defrost cycle matters because it is an operational setting with physical consequences. If an attacker changes the timing, duration, or target equipment, the result can be warmer storage temperatures, unstable cooling, alarms, and possible spoilage. In attacks against refrigeration and other OT systems, changing a routine control value may be enough to disrupt business without destroying hardware. Defenders should protect controller access, log configuration changes, and alert on unusual or unscheduled defrost events.