A newly discovered data exfiltration mechanism employs Ethernet cables as a transmitting antenna to stealthily siphon highly-sensitive data from air-gapped systems.

Dubbed “LANtenna Attack,” the novel technique enables malicious code in air-gapped computers to amass sensitive data and then encode it over radio waves emanating from Ethernet cables just as if they are antennas. The transmitted signals can then be intercepted by a nearby software-defined radioreceiver wirelessly, the data decoded, and sent to an attacker who is in an adjacent room.

The malicious code can run in an ordinary user mode process and successfully operate from within a virtual machine.Air-gapped networks are designed as a network security measure to minimize the risk of information leakage and other cyber threats by ensuring that one or more computers are physically isolated from other networks, such as the internet or a local area network.

The LANtenna attack is no different in that it works by using the malware in the air-gapped workstation to induce the Ethernet cable to generate electromagnetic emissions in the frequency bands of 125 MHz that are then modulated and intercepted by a nearby radio receiver. In a POC data transmitted over air-gapped received 200m apart.

Triggering the infection requires the deployment of the malware on the target network via any one of different infection vectors that range from supply chain attacks or contaminated USB drives to social engineering techniques, stolen credentials, or by using malicious insiders.

The researchers propose prohibiting the use of radio receivers in and around air-gapped networks and monitoring the network interface card link layer activity for any covert channel, as well as jamming the signals, and using metal shielding to limit electromagnetic fields from interfering with or emanating from the shielded wires.