The Caps Lock, Num Lock, and Scroll Lock LEDs on a keyboard can be used to exfiltrate data from a secure air-gapped system, academics from an Israeli university have proved. From a report: The attack, which they named CTRL-ALT-LED, is nothing that regular users should worry about but is a danger for highly secure environments such as government networks that store top-secret documents or enterprise networks dedicated to storing non-public proprietary information. he attack requires some pre-requisites, such as the malicious actor finding a way to infect an air-gapped system with malware beforehand. CTRL-ALT-LED is only an exfiltration method. But once these prerequisites are met, the malware running on a system can make the LEDs of an USB-connected keyboard blink at rapid speeds, using a custom transmission protocol and modulation scheme to encode the transmitted data. A nearby attacker can record these tiny light flickers, which they can decode at a later point, using the same modulation scheme used to encode it.