The Slammer hit on Super Bowl Sunday. Nimda struck one week after 9/11. Code Red had ripped through the system that summer. Moonlight Maze moved from the Russian Academy of Science and into the U.S. Department of Defense. A new form of warfare has broken out and the battleground is cyberspace. With weapons like embedded malicious code, probes and pings, there are surgical strikes, reverse neutron bombs, and the potential for massive assaults aimed directly at America's infrastructure -- the power grid, the water supply, the complex air traffic control system, and the nation's railroads. FRONTLINE investigates the threat of cyber war and reveals what the White House knows that the rest of us don't.