Hackers Steal Data From Air-gapped Computers by Turning Power Supply to Speakers

Researchers proposed a new method that enables attackers to steal data acoustically from air-gapped and audio-gapped systems.

Air-gapped computers are the computers isolated from the Internet and other local networks, the audio-less systems are considered to be audio-gapped.

Malware Manipulates Power Supply

Security researcher Mordechai Guri from the Ben-Gurion University of the Negev, Israel demonstrated the attack with a malware that exploits computer power supply unit (PSU) to play sounds and use them as a secondary speaker.

“The malicious code manipulates the internal switching frequency of the power supply and hence controls the sound waveforms generated from its capacitors and transformers.”

By using the attack method attackers can play audio streams from a computer even when audio hardware is disabled and speakers are not present.

“Our technique enables producing audio tones in a frequency band of 0-24khz and playing audio streams (e.g., WAV) from a computer power supply without the need for audio hardware or speakers. Binary data (files, keylogging, encryption keys, etc.) can be modulated over the acoustic signals and sent to a nearby receiver (e.g., smartphone).”

To launch the attacker, there is no additional hardware required or special privileges required, an attacker should first compromise the transmitter and receiver.

Then the malware in the infected computer gathers sensitive data such as files, keystroke logging, credentials, encryption keys and transfer them using the acoustic sound waves emitted by the computer’s power supply.

By using a nearby compromised device such as mobile phones attackers can decode the data and transfer to the server controlled by them.

Researchers told that this technique works with various types of systems: PC workstations and servers, as well as embedded systems and IoT devices that have no audio hardware at all.

“By using POWER-SUPPLaY attack, we could acoustically exfiltrate data from audio-less systems to a nearby mobile phone at a distance of 2.5 meters with a maximal bit rate of 50 bit/sec.”

Recently another paper published shows that attackers can exfiltrate sensitive information from the air-gapped computers by manipulating the brightness of the screen.

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