I doubt they are online. It would be an extremely idiotic thing to put those computers on the internet.
Like stated before, they are most likely on all closed circuit systems.
As I am a man of faith, I do not believe that we will be the demise of ourselves. I don't think "we" will cause our own "doomsday". When the Lord is ready for all of us, I don't think he'll let us know; we'll have no indication. He won't send out a letter to us all saying he's going to end it on XX/XX/XXXX. I'm ready for whenever he calls me.