A Briton who hacked into American defence networks and wiped out 300 PCs at a naval base faces trial in the US after being recommended for extradition by a British court.

Gary McKinnon, 40, of Wood Green, North London, whose attack was described by America as the biggest military hack of all time, said that he would contest the decision which must now be rubber-stamped by John Reid, the Home Secretary.

Mr McKinnon is alleged to have caused $700,000 (£370,000) worth of losses by hacking into the US computer systems over a period of a year. He insists that he never intended to harm US military capability and was merely researching UFOs.

Outside Bow Street Magistrates Court following publication of the decision today he vowed to fight on and claimed that if he was tried in Virginia he was "already hung, drawn and quartered."

He said: "[The hearing] went as expected and obviously the appeal process can now start. My intention was never to disrupt security, the fact that I logged on there and there were no passwords means that there was no security."

He said that he regretted his actions but added: "I was amazed at the lack of security and the reason I left not just one note but multiple notes on multiple desktops was to say 'this is ridiculous'."

Asked what he had been doing by hacking into US systems he told reporters that he had been looking for evidence of UFOs. He has described himself as a "bumbling hacker" who managed to exploit lax security policies and has never suggested he is a hacking mastermind.

Mr McKinnon’s solicitor Karen Todner said his legal team would appeal to Mr Reid and if refused there would be an appeal to the High Court to allow Mr McKinnon to be tried as a British citizen.

Lawyers said they were not surprised at the decision as it was consistent with Britain's extradition agreement with the US.

"The decision makes sense according to our extradition treaty with the US, which allows someone to be extradited for any crime which is punishable in both jurisdictions by a prison sentence of more than one year," Struan Robertson, an IT solicitor at Pinsent Masons, said.

"The only way out of it is if he faces the death penalty or if he can prove extradition is politically motivated, which he hasn't done. The fact that he may get 70 years in the US is irrelevant. The treaty makes an exception for capital punishment, but facing a harsh sentence is not in itself grounds to block extradition."

District Judge Nicholas Evans announced his decision today following a hearing last month where the court was told that McKinnon intended to gain access to the US’s military classified information network.

He was arrested in 2002 by the UK's National Hi-Tech Crime Unit for hacking into a series of computer networks used by the US Army, Navy, Air Force, and Department of Defence.

He is alleged to have deleted system files and logs from computers at US naval weapon station Earle at a critical time following the September 11 attacks. This rendered the base’s entire network – more than 300 computers - inoperable.

He fears he could be sent to Guantanamo Bay if extradited despite assurances he would not be tried by a military tribunal.

"As one person has said to me, most people in Guantanamo have not been proved to be terrorists but allegedly I directly attacked the military," he said.

But the US government said it had given assurances to the UK government that it would not make Mr McKinnon subject to the infamous Military Order Number One, which allows the US president to detain suspects indefinitely.

In a lengthy judgment, District Judge Evans rejected arguments including the possibility that Mr McKinnon could suffer prejudice at his trial because of his political opinions.

He added: "I readily accept, if convicted in the US, the probable sentence is likely to be appreciably harsher in the US than, in comparable circumstances, it would be in the UK.

"It must be obvious to any defendant that if you choose to commit a crime in a foreign country, you run the risk of being prosecuted in that country."

One security expert warned hackers to think carefully about the consequences of their actions. "There's a clear message here: don't mess with the Americans," Graham Cluley, a senior technology consultant for SophosLabs, said.

"If you or your malware hacks into a US government computer, you are really asking for trouble. Governments around the world are getting more serious about pursuing cybercriminals and are increasingly succeeding in catching the culprits."

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