Data can be stolen from an air gapped personal computer just by using variations in screen brightness. Researchers at Ben-Gurion University wrote a paper on it.

As the team defines them, “Air-gapped computers are systems that are kept isolated from the Internet since they store or process sensitive information.”

That they have come up with yet another discovery on how to wrest sensitive data from a computer came as no shock to Naked Security, which recognized that “Researchers at Ben-Gurion University of the Negev have made a name for themselves figuring out how to get data out of air-gapped computers. They’ve dreamed up ways to communicate using speakers, blinking LEDs in PCs, infrared lights in surveillance cameras, and even computer fans.”