יובל אלוביץ

Air-gapped computers are devices that are kept isolated from the Internet, because they store and process sensitive information. When highly sensitive data is involved, an air-gapped computer might also be kept secluded in a Faraday cage. The Faraday cage prevents the leakage of electromagnetic signals emanating from various computer parts, which may be picked up remotely by an eavesdropping adversary. The air-gap separation, coupled with the Faraday shield, provides a high level of isolation, preventing the potential leakage of sensitive data from the system. In this paper, we show how attackers can bypass Faraday cages and air-gaps in order to leak data from highly secure computers. Our method is based on exploitation of the magnetic field generated by the computer's CPU. Unlike electromagnetic radiation (EMR), low frequency magnetic fields propagate through the air, penetrating metal shielding such as Faraday cages (e.g., a compass still works inside a Faraday cage). Since the CPU is an essential part of any computer, the magnetic covert channel is relevant to virtually any device with a CPU: desktop PCs, servers, laptops, embedded systems, and Internet of Things (IoT) devices. We introduce a malware codenamed 'ODINI' that can control the low frequency magnetic fields emitted from the infected computer by regulating the load of the CPU cores. Arbitrary data can be modulated and transmitted on top of the magnetic emission and received by a magnetic 'bug' located nearby. We implement a malware prototype and discuss the design considerations along with the implementation details. We also show that the malicious code does not require special privileges (e.g., root) and can successfully operate from within isolated virtual machines (VMs) as well. Finally, we propose different types of defensive countermeasures such as signal detection and signal jamming to cope with this type of threat (demonstration video: https://www.youtube.com/watch?v=h07iXD-aSCA).