  he technology on infrared remote control is widely applied in human daily
life. It is also applied in the place with a top security level. Infrared
remote control signal is regarded as a simple, safe and clean resource that can
help us control the electrical appliances nearby. In this paper, we build
IREXF, a novel infrared optical covert channel from a well-protected air-gapped
network via a malicious infrared module implanted previously into a keyboard. A
malware preinstalled in the air-gapped PC receives the data from the malicious
infrared module to study the infrared surroundings in the air-gapped network.
Once a suitable appliance is found, infrared remote control commands will be
sent in a proper time. With the development of technology on Internet of
Things, more and more electrical appliances can access Internet. Those infrared
command signals exfiltrating out of the air-gapped network can be received by
an appliance without any malicious configuration. In our experiment, via a
smart TV set-top box, the rate of the covert channel can be up to 2.62 bits per
second without any further optimization. Finally, we give a list of
countermeasures to detect and eliminate this kind of covert channels.
