Researchers have proposed a new method that allows hackers to steal data from air-gapped and audio-gapped systems.
Air-gapped computers are computers that are isolated from the Internet and other local networks, and systems without sound are considered audio-gapped.
The malware manipulates the power supply
Security researcher Mordechai Guri from Ben-Gurion University of the Negev in Israel demonstrated the attack with malware that exploits a computer's power supply unit (PSU) to play sounds and use it as a secondary speaker.
“The malicious code manipulates the internal switching frequency of the power supply and therefore controls the audio waveforms produced by its capacitors and transformers.”
Using this attack method, attackers can play audio streams from a computer even when the audio hardware is disabled and there are no speakers.
"Our technique allows the generation of sounds in a frequency band of 0-24khz and the reproduction of audio streams (e.g. WAV) from a computer power supply without the need for audio hardware or speakers. Binary data (files, keyboards, encryption keys, etc.) can be modulated via the acoustic signals and sent to a nearby receiver (e.g. smartphone)."
To launch the attacker, no additional hardware or special privileges are required since an attacker would first have to compromise the transmitter and receiver.
The malware on the infected computer then collects sensitive data, such as files, keystrokes, credentials, and encryption keys, and then transmits them using acoustic sound waves emitted by the computer's power supply.
Using a nearby compromised device, such as a mobile phone, attackers can decode the data and transfer it to a server controlled by them.
The researchers said 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.
"Using the POWER-SUPPLaY attack, we could transmit audio data from silent systems to a nearby mobile phone at a distance of 2.5 meters at a maximum bit rate of 50 bits/sec."
Recently, another paper published shows that hackers can infiltrate sensitive information of air-gapped computers by manipulating the screen brightness.
