Researchers turn an air-gapped system into a Wi-Fi transmitter

Malware planted on computers could use electromagnetic signals from memory to transfer data wirelessly

Researchers have found a way to turn a RAM module in an air-gapped computer into an ad-hoc Wi-Fi card in order to transfer data from a computer that would otherwise have no connection to the internet.

The exploit, dubbed 'Air-Fi', can transform an air-gapped computer into a device that uses DDR SDRAM buses “to generate electromagnetic emissions in the 2.4 GHz Wi-Fi bands and encode binary data on top of it”, according to a research paper published by scientist Mordechai Guri, at the Ben-Gurion University of the Negev, Israel.

Air-gapped systems are designed to be isolated from external unsecured networks, which means they're disconnected from the internet, and devices or systems capable of accessing the internet. They often find use in highly sensitive environments, such as sites operated by the military or government agencies.

Electronic components generate electromagnetic waves when the electrical current passes through them, the same process that's used in Wi-Fi networks. Guri’s idea was to install malware on an air-gapped system that would adjust the electrical current running through the RAM to generate 2.4GHz radio signals.

By using this technique, Guri was able to pick up the wireless signal using any device with Wi-Fi, such as a smartphone or even an IoT device. For any memory module that was unable to transmit at that frequency, the malware would overclock or underclock the memory frequency via the BIOS/UEFI firmware.

Guri managed to transfer data from the RAM modules at up to 100 bytes per second within a radius of few meters. The hack can work on any operating system or even a virtual machine, without the need for the air-gapped computer to have any Wi-Fi transmitter installed.

Guri pointed out there are a number of countermeasures that could be taken to prevent such an attack. These range from banning any type of Wi-Fi receiver from near an air-gapped device, software, and hardware signal jamming, or placing an air-gapped computer in a faraday cage.

Planting malware on an air-gapped machine would also likely require physical access to the system.

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