Dubbed USBee, the technique turns a computer’s USB ports into mini RF transmitters by modulating the data fed at high speed to plugged-in devices. By banging out a string of ‘0’ bits to a USB port, the voltage changes in the interface generate detectable emissions between 240MHz and 480MHz, according to Guri.

Next, by writing sequences of ‘0’ and ‘1’, we’re told you can create a carrier wave from the rapid voltage changes on the interface’s data pins. You can then use binary frequency shift keying (B-FSK) to encode useful information into the wave.

Guri reckons you can beam 80 bytes per second over the air using this technique, which is fast enough to send a 4,096-bit crypto key to a nearby receiver in less than 10 seconds.

Source: USBee stings air-gapped PCs: Wirelessly leak secrets with a file write