A researcher in Israel devised the attack as a way to steal data from 'air gapped' PCs, or computers that have been sectioned off from the internet.
A security researcher has developed a way to pluck data from a highly guarded PC by manipulating the hardware’s power supply to generate radio waves and secretly transmit the stolen data to a nearby smartphone.
The research comes from Mordechai Guri at Israel’s Ben-Gurion University of the Negev. Over the years, Guri has helped devise numerous ways to exfiltrate data from air-gapped PCs, or highly protected computers that are deliberately isolated from the internet.
In a new research paper(Opens in a new window), Guri shows that it’s possible to use malware to rig a PC’s power supply to transmit data from the computer, such as documents, keystrokes, and passwords. The reason is that a power supply can generate radio signals in the low-frequency band between 0 to 60kHz, which can be decoded.
“By regulating the workload of the CPU, it is possible to govern its power consumption and hence control the momentary switching frequency of the SMPS (switch-mode power supplies),” he writes in his paper. “The electromagnetic radiation generated by this intentional process can be received from a distance using appropriate antennas.”
I tip my hat to the researcher 
