100% Secure "Second Internet" - The only way?

[Nitestick]

Regardless there will have to be some type of internet interface, so somewhere along the line you are going to have a SAN or switch that connects the network to the rest of the word. Which then would be a point of attack.

IMO i believe cyber security is much easier than physical security. You are right, there are probably hundreds of attacks every week, but imagine if there was a physical location that someone could just run a car into and it would take down a power grid.

Physical security versus electronic security was part of what I was trying to allude to above. For example, IMHO it's easier to place packet sniffers somewhere in a wired network that isn't encrypted (as is often the case with private networks) than it would be to break into a WPA2 wireless network.