>You can use memory module busses, power/camera/keyboard LEDs, fan speeds, ultrasound emitted from speakers...it's not very interesting, at this point. This is

>You can use memory module busses, power/camera/keyboard LEDs, fan speeds, ultrasound emitted from speakers...it's not very interesting, at this point. This is why classified information is typically handled in a SCIF (Sensitive Compartmentalized Information Facility, "skiff"). It's an implementation of defense-in-depth; the idea that an adversary must breach several layers of physical and digital security to compromise your secrets. These attacks are of little use at the National Defense level because they would require installing e.g. a receiving antenna within 6 feet of a compromised machine. In other words, to leverage this attack you'd have to achieve a total collapse of your adversary's classified processing security posture. Well, if you can effect that then you don't need this attack.