From: Strategy Page
An American government official, Xiafen Chen, was arrested in October and charged with supplying China with classified data about American dams. This is part of a Chinese effort to collect detailed data on American infrastructure and other economic targets to support preparations for Internet based attacks on these facilities in wartime, or anytime. Xiafen Chen and her husband moved to the U.S. from China in 1992 and later became American citizens. The FBI found emails in which Xiafen Chen discusses the data she took from U.S. government databases and passed to senior Chinese officials.
The U.S. government has been aware of this Internet threat for over a decade and has been trying to develop a way to respond to a serious Cyber War attack, one in which the attacker does not reveal who they are. The data the Chinese received from Xiafen Chen could be used for such an attack.