Detectives have arrested an 18-year-old man as part of the investigation into hacking groups Anonymous and LulzSec.
The alleged hacker, who is said to use the online nickname "Topiary" and present himself as a spokesman for the groups, was held in the Shetland Islands, Scotland Yard said.
Police are also searching a house in Lincolnshire and interviewing a 17-year-old boy under caution in connection with the inquiry.
The 18-year-old was arrested by officers from the Metropolitan Police Service's central e-crime unit in a swoop linked to an ongoing investigation into hacking and distributed denial of service attacks, where websites are flooded with traffic to make them crash, against international companies and intelligence agencies believed to be carried out by Anonymous and LulzSec.
The suspect is currently being transported to a central London police station while detectives search the home in the Shetland Islands where he was held.
Scotland Yard said in a statement: "The man arrested is believed to be linked to an ongoing international investigation into the criminal activity of the so-called 'hacktivist' groups Anonymous and LulzSec, and uses the online nickname 'Topiary' which is presented as the spokesperson for the groups."
The 17-year-old has not been arrested, police added.
LulzSec has previously claimed responsibility for hacking attempts on the UK's Serious Organised Crime Agency (Soca), the US Senate, the CIA and The Sun newspaper.
Ryan Cleary, 19, of Wickford, Essex, was charged last month with five offences under the Criminal Law and Computer Misuse Acts, including an alleged hacking attack against Soca's website.
