Moonlight Maze, a cyber attack targeting the Pentagon, was discovered in 1999 and believed to be undertaken by expert hackers from the Russian Academy of Sciences (a government-supported body that has close links to the Russian military). According to reports, they broke into DoD computer networks and extracted information that may have included classified naval codes and data on missile-guidance systems. DoD officials described the intrusions, which occurred as a series of attacks over a two year period, as sophisticated, patient, and persistent.