Experts from the Ben-Gurion University of the Negev (Israel) have demonstrated a way to steal data from a physically isolated system through a power supply. During the POWER-SUPPLaY attack, the scientists managed to turn the computer's power supply into an audio speaker capable of invisibly transmitting data from the attacked host using sound waves.
According to the head of the study, Mordechai Guri, POWER-SUPPLaY allows data to be stolen from devices without speakers. Using specially designed malware, the researchers turned the computer's power supply into a primitive audio speaker that generates basic sound waves. It should be noted that the purpose of the study was only to examine the method of extracting data from a physically isolated system, but not the methods of infecting it with malware.
As Guri explained, an attacker can manipulate an electrical current in the power supply's capacitors and cause a phenomenon known as a "singing" capacitor. With this phenomenon, a capacitor generates sound waves when alternating current with different frequencies passes through it. By controlling the frequency of the AC current, malware can manipulate sound waves and thus hide data in them.
The sound signals generated by the "singing" capacitor can be received by a nearby receiver (for example, a smartphone). The device decodes the signal and will transmit the intercepted data to the attacker via the Internet.
A distinctive feature of POWER-SUPPLaY is that malware does not require any special privileges. The attack works on PCs, servers, embedded systems and IoT devices without radioelements. The disadvantages of the attack are slow data transfer, the inability to transfer data over long distances (the maximum distance is 6 m) and the effect of background noise on the quality of sound waves.
The "singing" of a capacitor is one of the descriptions of the piezoelectric effect. It is actually a vibration of a capacitor on a PCB causing a faint noise.
The piezoelectric effect is the effect of the occurrence of polarization of a dielectric under the influence of mechanical stresses.
