Updated:01:17 AM CET Nov,05

Basically, modern CPUs, GPUs, and motherboards have built-in thermal sensors such as temperature diodes. These exist primarily for thermal management, allowing the system to spin up fans, throttle clocks, or shut down if it overheats. Some studies, however, have demonstrated that it is possible to maintain a very low-bandwidth covert channel between two air-gapped computers, who can talk to each other by running one of the CPUs hot and then using the ensuing thermal variations as a code that the other computer can interpret.