"Attacks like Stuxnet, the computer worm deployed against an Iranian nuclear facility a decade ago, shattered the myth that air-gapped systems are impenetrable fortresses."

source: https://www.cyberscoop.com/duo-labs-air-gap-radio-mikhail-da...

Links to: https://duo.com/labs/research/finding-radio-sidechannels

It wasn't really air-gapped if someone plugged an USB in it, was it ;)

I'm aware of the "over the air" methods to _read_ data from air-gapped systems (The blinking hard-drive light!), however I was referring to doing damage to industrial systems running legacy software, where you usually find this (think a big machine with a "terminal" attached to it that just controls the hardware and has no inputs).

That's exfiltration, not infiltration.