Scientists says Hack an offline PC by listening to its fans

A team of researchers claim they've developed malware that can extract data from an isolated computer with no internet connection, camera or audio hardware—all by using sounds generated by the machine's processor and cooling fans.

In a new paper, researchers at Israel's Ben Gurion University describe an attack meant to be used against isolated or “air-gapped” machines that wouldn't normally be accessible. While others have demonstrated ways of doing this using ultrasonic waves coming from a machine's speakers, the method the Israeli researchers describe works by controlling and listening to the speed of the machine's fans and CPU, and doesn't require it to have any speakers, cameras or other hardware.

“Using our method we successfully transmitted data from [an] air-gapped computer without audio hardware, to a smartphone receiver in the same room,” the researchers says.

It's not the first time that audio signals have been used to extract data from air-gapped machines. Previous malware demonstrations have shown that PCs' internal and external speakers could use similar techniques to broadcast data signals via audio to capture devices.

We show that our method can also be used to leak data from different types of IT equipment, embedded systems, and IoT devices that have no audio hardware, but contain fans of various types and sizes.”

The malware, which infects machines via a sneaky double-agent wielding a USB stick, works a bit like morse code. Once installed, it locates data on the machine and transmits it by controlling the speed of the machine's CPU and cooling fans, creating acoustic waveforms that are then received and deciphered by a nearby listening device.

This capability led some to think that, to make computers truly secure, they need to be audio-gapped (with all audio speakers disabled) in addition to being air-gapped (cut off from any non-secure networks) – but the new approach shows that even audio-gapping may not be enough in some circumstances to entirely lock down a PC.

The researchers say they were able to exfiltrate data at up to 900 bits/hour, with a listening device placed within 8 meters of the machine. While that's hardly ideal for downloading a new Taylor Swift album, it's just fine for stealing passwords and encryption keys.

Source: MOTHERBOARD

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