Iranian muslims were surfing the Navy Marine Corps Internet for over 4 months that we know about. They made their way into the unclassified network in the usual way of hackers and other cyber ne'er-do-wells and had a fine time examining all the content they could suck through their cyber hookahs. The ugly little secret is that once you're in to the NMCI network you can pretty much roam at will through the largest intra-net in the world. Once you're in and attach the data vacuum all you have to do is suck, a lot. The code breakers and other hackers will get you into the password protected sites and files and you can read them at your leisure.
Nothing happens without a reason. I hope the Iranians enjoyed reading the public mail. Sometimes one has to remember that the Soviets didn't suddenly come to the realization that they were competing so far out of their league it wasn't even a contest. Somebody had to help them to see for themselves just how disparate was the correlation of forces. There's enough on the unclassified networks to make it pretty clear that the US could do a complete take down of the Iranian forces and impose a regime change in less than a week. If it wanted to. It doesn't hurt anybody to let them know that before they make it necessary.