I've worked in utilities before, and sometimes it's not possible to airgap those systems. After all, someone needs to login and update and performance maintenan

I've worked in utilities before, and sometimes it's not possible to airgap those systems. After all, someone needs to login and update and performance maintenance on those SCADA systems. And it's pretty expensive to fly those people in, and sometimes not possible. But there are optical routers that guarantee one way only access to networks. My favorite method is a switch, with the power supply connected to a physical timer. Once the time's up, the power supply is cut, and that device no longer is accessible. Quite ingenious really.