Researchers at Ben-Gurion University of the Negev in Israel have disclosed yet another method that can be used to exfiltrate data from air-gapped computers, and this time it involves the activity LED of hard disk drives (HDDs).

Many desktop and laptop computers have an HDD activity indicator, which blinks when data is being read from or written to the disk. The blinking frequency and duration depend on the type and intensity of the operation being performed.