Prosecutor Paul McNulty alleged that McKinnon, known online as "Solo," had perpetrated "the biggest hack of military computers ever". He was named as the chief suspect after a series of electronic break-ins occurred over 12 months at 92 separate US military and Nasa networks.Why did he do it?
McKinnon was also accused of hacking into the networks of six private companies and organisations.
It is alleged that he used software available on the internet to scan tens of thousands of computers on US military networks from his home PC, looking for machines that might be exposed due to flaws in the Windows operating system.
Many of the computers he broke into were protected by easy-to-guess passwords, investigators said. In some cases, McKinnon allegedly shut down the computer systems he invaded.
Friends said he was desperate to prove that the Americans had mounted a huge cover-up to deny his belief that aliens had visited earth.His mom is quoted as saying she is sorry she bought the complete X-Files set for her son for Christmas.