If you control the blinking of the led you have established a very low bandwidth communication channel.

Ohhh I misunderstood; I thought they were stealing data by simply observing the blinking LED, not that they had infiltrated the computer and were controlling the LED.

Allmost (or all?) of those attacks are only possible, if the target computer is infected. And the scenario is that the virus wants to send data out, to a nearby decice which is also infected.

Which is why this is "exfiltration", not "infiltration".

The term "exfiltrate" implies that the data is being "pushed" or otherwise sent outward from the machine, as opposed to being harvested from the outside.

Thank you, because you wrote this, I too now understand what they meant. My train of thought was apparently on the same track as yours!

Basically the idea is that air gapped is still not secure. If someone plugs in a foreign flash drive into a computer that is air gapped one would think the data can’t leave the secure machine. With these methods though, it’s clear that any hardware observable to the outside world can be used to exfiltrate data

Well, I think anyone could have thought of the screen or speakers or, well the usb you achieved to plug to get data out of a computer. You have no network but I doubt you can consider airgapped a pc you just plugged a usb device into. Why not plug a mini wifi chip then ?

"Guri's research doesn't look at ways of compromising and planting malware on these super-secure systems" ... "malicious code planted on an air-gapped system can control the speed at which fans work"

It's about how to get data out once you've already compromised the machine. You control the blinking of the LED to match match the data you want to capture out.