The technique was developed by  Mordechai Guri, the head of R&D at the Ben-Gurion University of the Negev, in Israel.

Dubbed AIR-FI the system uses the theory that an electronic component generates electromagnetic waves. Since Wi-Fi signals are radio waves and radio is basically electromagnetic waves, Guri argues that malicious code planted on an air-gapped system by attackers could manipulate the electrical current inside the RAM card in order to generate electromagnetic waves on the Wi-Fi signal spectrum (2,400 GHz).

In his research pape with the catchy title AIR-FI: Generating Covert WiFi Signals from Air-Gapped Computers, Guri shows that perfectly timed read-write operations to a computer's RAM card can make the card's memory bus emit electromagnetic waves consistent with a weak Wi-Fi signal.

This signal can then be picked up by anything with a Wi-Fi antenna in the proximity of an air-gapped system, such as smartphones, laptops, IoT devices, smartwatches, and more.

Guri says he tested the technique with different air-gapped computer rigs where the Wi-Fi card was removed and was able to leak data at speeds of up to 100 b/s to devices up to several meters away.