* air-gap malware can be designed to communicate secure information acoustically, at frequencies near or beyond the limit of human hearing.
* In 2014, researchers introduced ″AirHopper″, a bifurcated attack pattern showing the feasibility of data exfiltration from an isolated computer to a nearby mobile phone, using FM frequency signals.
* In 2015, "HELLONE", a covert signaling channel between air-gapped computers using thermal manipulations, was introduced. "BitWhisper" supports bidirectional communication and requires no additional dedicated peripheral hardware.
* Later in 2015, researchers introduced "GSMem", a method for exfiltrating data from air-gapped computers over cellular frequencies. The transmission - generated by a standard internal bus - renders the computer into a small cellular transmitter antenna.
