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16 September 2024

Air-Gapped Networks Vulnerable to Acoustic Attack via LCD Screens

Nate Nelson

A newly devised covert channel attack method could undermine diligently devised air gaps at highly sensitive organizations.

In industrial control systems security, the term "air gap" is contested. It typically describes a total physical separation between networks — a literal gap through which no Wi-Fi signals, wires, etc., can pass. The most critical military, government, and industrial sites use air gaps to prevent Internet-based cyber threats from penetrating the kinds of networks that protect state secrets and human lives.

But any medium capable of transmitting information can, in theory, be weaponized to transmit the bad kind. Mordechai Guri of Israel's Ben-Gurion University has long researched ways of crossing air gaps with sound waves: via computer fans, hard disk drives, CD/DVD drives, and more. His latest attack scenario, "Pixhell," enables data theft using sounds produced by specially generated, rapidly shifting bitmap patterns on an LCD screen.

How Pixhell Works

It's midnight, and everyone working at the top secret intelligence facility has long gone home for the night, when all of a sudden a computer screen flashes with what appears to be random noise, as if it's missing a signal. It isn't missing a signal — the apparent noise is the signal.

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