Gary McKinnon, 39, an unemployed man from north London, was arrested Tuesday night, the agency said.
McKinnon, known as "Solo" in the hacking world, was set to appear Wednesday before the Bow Street Magistrates Court on an extradition warrant from the U.S. government, Scotland Yard said.
According to the warrant, McKinnon gained illegal access and made unauthorized modifications to 53 computers belonging to the U.S. government, including computers from the Department of Defense and the National Security Agency, between February 2001 and March 2002.
If extradited and found guilty in the United States, he faces five years in prison for eight crimes he wasin 2002. Among the charges, McKinnon is suspected of stealing administrator identities, deleting 1,300 user accounts and copying a file containing usernames and encrypted passwords.
Dan Ilett of Silicon.com reported from London.