Infected memory stick.
That's how it got to the Space Station. But if the virus was transmitted through the network connections then it shows just who was working with the Iranians on their nuke program. Not that this should have been any big secret.
Infected memory stick>>>>>>>>
That’s how you do it. If I ran a super secure something there would be no USB ports or DVD/CD players on the computers. There are other entry ways I would also cut off. Obviously no internet connection