When President Ronald Reagan was relaxing at Camp David in 1983, he happened to see the film War Games, starring the young Mathew Broderick as a "tech-whiz teenager" who thinks he's playing a computer game. It turns out that the kid has unwittingly hacked into America's real-world defense system, and he almost starts World War III. President Reagan's reaction to that film begins the book, Dark Territory: The Secret History of Cyber War, by Pulitzer-Prize winning reporter and author Fred Kaplan, who's currently national security correspondent for Slate.