Actually the virus sent to Iran was more subtle....
The first one what it did was change the feedback from the motor speed controllers on their Uranium seperation centrifuges, so that the computer was believing the motor speed was significantly different than it was and this intentionally incorrect feedback caused the motor controllers to damage the motors and incorrectly seperate the material they were processing.
It only affected certain models of electronic motor controllers.
Motor controllers designed in the Ukrane and manufactured in China
And it kept re-infecting computers.
Combined with that when the head IT guy in Iran got close to a solution "somebody"rode up on a motorcycle and stuck a chunk of
steel plate backed with a sheet of explosive (Look up "Misznayâ€“Schardin effect") to the side of his car which blew the chunk of steel plate through his car and incidentally through the IT guy himself....
the virus was distributed through ISB drives that were filled with MP3 files or AVI or MP4 Feature films and abandoned at bars, cafes public restrooms.
It was only natural that one of these drives would eventually find it's way into isolated secure systems that are not connected to the net in any way, shape or form.