Gary McKinnon

But Mitnick has since been superseded by McKinnon, who managed to hack into the Pentagon computers and leave the message “Your security is crap”. Between 2001 and 2002 – sensitive times for America – he repeatedly hacked US military and NASA computers from his base in London, deleting files and changing passwords. At one point he caused a 24-hour shutdown and caused munitions trucks to be stopped. He also left an anti-American message: “US foreign policy is akin to Government-sponsored terrorism these days … It was not a mistake that there was a huge security stand down on September 11 last year … I am SOLO. I will continue to disrupt at the highest levels.” He was arrested in 2002 and is currently imprisoned in Britain, although the US continues to request his extradition. A skilled but also very dangerous hacker who was stopped before he managed to cause a military disaster.