It's called the National Cyber Range and it's being constructed by the Pentagon's always interesting and usually somewhat disquieting Darpa group. It's basically a dummy internet being built to test cyber defenses by simulating a broad range of cyber attacks. The system should be up and ready to go some time next year. Among the bugs still in the system: Lockheed Martin is helping build the thing and that company was the target of a recent hack. Whoops.
Well, as long as it never connects to the actual internet, everything should be fine. And if it does, that will be a TOTAL DISASTER. Good luck, everyone!