A British man wanted in the US for allegedly hacking into nearly 100 computer networks operated by the US military and Nasa has said he will fight any attempt to extradite him.

We can only presume that the motivation is political and that it is proposed to make an example of Mr McKinnon

Mr McKinnon's lawyer Karen Todner

Gary McKinnon, the 36-year-old an unemployed computer programmer from Hornsey in north London, is accused of what is described in the US as the biggest military computer hack of all time, and could face a lengthy sentence in US custody if convicted.

His lawyer, Karen Todner, said that Mr McKinnon could have been charged by British authorities but instead they had decided to permit US authorities to begin extradition proceedings.

"We can only presume that the motivation is political and that it is proposed to make an example of Mr McKinnon," she said.

"We shall oppose any extradition application in connection with our client."

Severe disruption

Mr McKinnon has been indicted in the US states of Virginia and New Jersey on eight counts of computer-related crimes in 14 different states.

This is an incredibly sophisticated cyber criminal...he was a very busy guy

Newark US Attorney Christopher Christie

Over one year he allegedly stole passwords, deleted files, monitored traffic and shut down computer networks on military bases from Pearl Harbour to Connecticut, causing what the US military said were severe disruptions.

It is estimated he caused damage of up to $1m.

Two of the alleged computer break-ins were at the Pentagon, and he also allegedly crashed a system of 300 computers at a New Jersey navy facility, Earle Naval Weapons Station in Colts Neck, shortly after the 11 September attacks.

So concerned were naval staff that the network was in effect shut down for a week.

Mr McKinnon, known by the internet nickname of "SOLO", is also alleged to have hacked into space agency Nasa.

He was arrested in Britain in March by elite crime squad officers after Nasa suspected him of breaking into their systems, released in August and then questioned again before being set free.

His current whereabouts are unknown.

'Sensitive' information

The authorities said no classified information had been accessed, although they admitted that "sensitive" information may had been read.

"This is an incredibly sophisticated cyber criminal," said Newark US Attorney Christopher Christie. "He was a very busy guy."

They do not believe the hacking was terrorist-related and he is thought to have acted alone.

US Attorney Paul McNulty alleged that Mr McKinnon searched for computers that were "open for attack" - possibly through publicly accessible websites.

It is alleged he would then install hacker tools, including a remote administrator programme that could not be detected and which gave him control of the computer.

With these, he allegedly accessed other computers from which he copied files and deleted critical systems files, Mr McNulty said.

He added that, if convicted, Mr McKinnon faces up to10 years in prison and fines of $250,000 on each of the eight counts against him.