The People's Liberation Army (PLA) of China calls the electromagnetic spectrum "the fifth domain of battle space," putting cyberspace on an equal footing with ground, air, sea, and space. Augmenting PLA efforts is a legion of civilian researchers and hackers whose efforts are ostensibly directed at repelling electronic intruders. Now that Pandora's box is open, the United States fears that it, too, may someday be on the receiving end of an effective attack. Hackers in China have gathered gigabytes of data on industrial secrets, military hardware, and government strategy for political negotiations.