A British hacker goes before magistrates at Bow Street today to fight extradition proceedings to the US.

Gary McKinnon, 39, of Wood Green, north London, was arrested by officers from the Metropolitan Police Service Extradition Unit on Tuesday night and is charged with the "biggest military computer hack of all time", according to Paul McNulty, the US Attorney for the Eastern District of Virginia.

It is claimed that in 2002, McKinnon hacked into computer networks belonging to Nasa, the US army, US navy, Department of Defense and the US Air Force, and that one of the systems belonged to the Pentagon.

"Cyber-criminals will often target high-profile systems that are known to contain critical data, and security breaches like this should definitely serve as a wake-up call," said Sara Buttle, corporate communications manager at RSA Security.

"Not all hackers are technical geniuses, and it can be surprisingly easy for them to sabotage a computer system. Fortunately, it is also relatively simple to protect most networks, for example by using stronger authentication and password procedures."

Technical experts have derided suggestions that McKinnon is a hacking genius. Some have claimed that he accessed US military systems by checking with users who had the word 'password' as their log-in. 

McKinnon faces years in prison if extradited to the US. McNulty is known for demanding maximum sentences and has been part of many high profile cases, including American Taliban member John Walker Lindh; Zacarias Moussaoui, the first person to face criminal charges in the 11 September attacks; and convicted spy Robert Hanssen.