To the United States, he is a seriously dangerous man who put the nation's security at risk by committing "the biggest military computer hack of all time."
But Briton Gary McKinnon says he is just an ordinary computer nerd who wanted to find out whether aliens and UFOs exist.
During his two-year quest, McKinnon broke into computers at the Pentagon, NASA and the Johnson Space Center as well as systems used by the U.S. army, navy and air force.
U.S. officials say he caused $700,000 worth of damage and even crippled vital defense systems shortly after the September 11 attacks.
The unemployed computer programmer is now battling extradition to the United States, where, if found guilty, he faces up to 70 years in jail and fines of up to $1.75 million. His lawyer fears he could even be sent to Guantanamo Bay.
It's all a far cry from how he first got into hacking: watching a film about a teenage boy who breaks into a military central computer and almost starts World War Three.
"I had seen the film 'War Games' and I do remember clearly thinking at the time, that's amazing -- a great big military computer system and a young, spotty teenager," the softly spoken 39-year-old told Reuters in an interview.