Gary McKinnon, 35, appeared at Bow Magistrate's Court on charges he gained unauthorised access to 97 U.S. government computers.
McKinnon claims the damage he caused was minimal but U.S. authorities indicate costs of up to £370,000. It is claimed McKinnon 'owned' computers belonging to the army, navy, airforce, Nasa and the U.S. Department of Defense.
If convicted McKinnon could face up to 70 years in jail. Acting on behalf of the U.S. government Mark Summers claimed that McKinnon acted from his own computer in London and attempted to influence U.S. government policy by sending intimidating and coercive messages.
McKinnon allegedly left messages criticising U.S. foreign policy and deleted important files at the Earle, a US naval weapons base.
McKinnon has publicly admitted some aspects of the hack, claiming he was only looking for evidence of UFOs and expressing some surprise at the ease with which he was able to gain access to military systems.
The extradition hearing has been adjourned until October 18 so that McKinnon's lawyers can arrange a defence. In that time he is not allowed to leave the country, obtain any travel documents or gain access to the internet.