A teenager has been arrested in a joint Scotland Yard and FBI investigation into the hacking of websites.
The 19-year-old man was held during a raid at a house in Wickford, Essex.
On Monday the UK's Serious Organised Crime Agency (Soca) took its website offline after it was attacked by Lulz Security hackers.
Scotland Yard would not confirm the arrest was connected but did say that it followed a series of distributed denial of service (DDoS) attacks.
The raid in Essex had been a "pre-planned, intelligence-led" operation, it said.
The teenager was arrested under the Computer Misuse Act and Fraud Act and is being questioned at a central London police station.
He was arrested by the Metropolitan Police's e-crime unit.
A Scotland Yard spokesman said: "The arrest follows an investigation into network intrusions and distributed denial of service attacks against a number of international business and intelligence agencies by what is believed to be the same hacking group.
"Searches at a residential address in Wickford, Essex, following the arrest last night have led to the examination of a significant amount of material. These forensic examinations remain ongoing."
Scotland Yard is co-operating with the FBI as well as Essex Police.
An FBI spokesman said it had no comment "at this time".