> I've known companies that physically removed all USB ports from laptops. I've encountered desktop setups where various ports were filled with epoxy, rather t

> I've known companies that physically removed all USB ports from laptops. I've encountered desktop setups where various ports were filled with epoxy, rather than being removed. A co-worker once bridged an air gap using audio. I forget most of the details, but his POC used staccato clicks to evade notice rather than supersonic frequencies (a prior unsuccessful attempt IIRC tried modulating the vsync on CRTs in lieu of speakers, which gave me a headache and prompted me to track it down since I could hear it even though no-one else could).