I don’t know what the US government runs on its most secure systems but with all the money we pay in taxes, I hope it’s not Windows, Linux, or macOS. I hope they scooped up some 80’s operating system no one would ever suspect and kept it going in parallel. Good luck hacking into a system with a fully custom version of Business Operating System that runs on 64 bit Motorola processors no one knows about but the CIA’s sysadmins.
I know in reality they probably run Windows Vista on 12 year-old laptops or some shit and get hacked all the fucking time but I’d like to think someone had enough sense to not do that.