@walterbays I visited the company that manages the Australian Lottery a while back. They were totally disconnected from the internet. There were separate stations available that were connected to the internet, but not to the internal network.
It made for challenges supporting software for them.
I have no idea if they still have that disconnected requirement
@S_r_stone I also had support challenges. I assigned an engineer to do some software maintenance in the vault. He was not allowed to tell anyone - not even me, his manager - what he was doing. Status reports were: How is it going? Fine, maybe one more week. Good thing he was someone I trusted so well.
It reminds me of how NASA treated computer security early in my career. Secure meant the vault inside a Faraday cage with no wires passing the boundary, nobody going in or out with any electronic device whatsoever, and of course with security clearance.