The hackers targeted retired Admiral Mike Mullen, the former chairman of the Joint Chiefs of Staff. Mullen is currently teaching WWS 318: U.S. Military and National and International Diplomacy and will teach an unnamed graduate seminar in the spring. He did not save or view classified information on his personal computers, aides say. One official says evidence gathered by the FBI points to China as the origin of the hacking, and that it appeared the perpetrators were able to access a personal email account of Mullen.
Source: https://thehackernews.com/2012/12/hackers-hit-former-us-military-chief.html