This paper presents AirKeyLogger - a novel radio frequency (RF) keylogging attack for air-gapped computers.Our keylogger exploits radio emissions from a computer’s power supply to exfiltrate real-time keystroke data to a remote attacker. Unlike hardware keylogging devices, our attack does not require physical hardware. Instead, it can be conducted via a software supply-chain attack and is solely based on software manipulations. Malware on a sensitive, air-gap computer can intercept keystroke logging by using global hooking techniques or injecting malicious code into a running process. To leak confidential data, the processor’s working frequencies are manipulated to generate a pattern of electromagnetic emissions from the power unit modulated by keystrokes. The keystroke information can be received at distances of several meters away via an RF receiver or a smartphone with a simple antenna. We provide related work, discuss keylogging methods and present multi-key modulation techniques. We evaluate our method at various typing speeds and on-screen keyboards as well. We show the design and implementation of transmitter and receiver components and present evaluation findings. Our tests show that malware can eavesdrop on keylogging data in real-time over radio signals several meters away and behind concrete walls from highly secure and air-gapped systems.