Gary McKinnon, the UK citizen accused of the biggest military hack in history, will be extradited to the US where he faces a possible life sentence.

The former hacker's appeal against extradition was rejected by the House of Lords this morning.

McKinnon is now expected to continue his fight against extradition in the European courts. The case has been rumbling through the appeals process for three years.

According to the prosecution, McKinnon hacked into and disrupted numerous US military computers in 2001 and 2002 from his bedroom in North London.

McKinnon has consistently claimed that he is "a bumbling hacker" who was never a threat to security, and that he was only looking for UFO files that he believed the US government was keeping under wraps.

US prosecutors have offered McKinnon, aka 'Solo', a plea bargain. If he pleads guilty to two of the charges he will receive a four-year sentence. Otherwise, the 42 year-old faces a possible 70 years if found guilty of all the charges.

The decision should act as a warning to other cyber-criminals, according to IT security firm Sophos.

"The US is making a clear stand that anyone making any attempts to compromise its computers and data will face the consequences," said Graham Cluley, senior technology consultant at Sophos.

"In McKinnon's case, this means that they are not going to give up until they have their man.

"Any form of hacking is illegal and should be punished as such, and hacking into US government networks is bound to come with harsh repercussions. Anyone thinking about engaging in these types of activities in the future should think twice."