A fifth person has been arrested as part of an ongoing probe into the TalkTalk cyber attack, the Metropolitan Police said.
The 18-year-old was taken into custody after police raided a property in Llanelli, south Wales, on Tuesday and was being held at the Dyfed Powys police station on suspicion of blackmail.
Four other people have previously been arrested during the investigation, including a 15-year-old boy from Northern Ireland who was released on bail pending further enquiries.
Two 16-year-old boys and a 20-year-old man have also been arrested since the cyber attack last month.
During the attack hackers accessed the details of 156,959 customers and 15,656 bank account numbers.
It was the third in a spate of cyber attacks affecting TalkTalk in eight months, with incidents in August and February resulting in customers’ data being stolen.
In a statement the Metropolitan Police said the investigation was continuing.
It is being carried out by the Met’s cyber crime unit, the Police Service of Northern Ireland’s cyber crime centre and the National Crime Agency.
Jesse Norman, chairman of the Commons Culture, Media and Sport Select Committee, is leading an inquiry into the alleged data breach.
Officers are investigating a ransom demand sent to the phone and broadband provider by someone claiming to be responsible and seeking payment. The firm said it was not sure if the message was genuine.