A 19-year-old British youth, Ryan Cleary, has been arrested on suspicion of involvement in LulzSec, an international hacking group that has launched a wave of cyber attacks on high-profile organisations.

Cleary, from Wickford in Essex, was detained in a "pre-planned intelligence-led operation” in cooperation with the FBI, the Metropolitan Police said.

He was being questioned at a central London police station on suspicion of Computer Misuse Act and Fraud Act offences. Computer forensics specialists were also examining a "significant amount of material" seized from his address.

LulzSec's victims have included Sony, the US Senate, the NHS and security companies linked to the FBI.

On Monday it hit the Serious Organised Crime Agency’s website with a Distributed Denial of Service attack, flooding its servers and forcing it offline.

Full story: The Telegraph