A teenager has become the sixth person to be arrested in connection with the alleged data theft from TalkTalk.
A 19-year-old man from Staffordshire was arrested on suspicion of computer misuse offences on Wednesday.
He handed himself at a police station in the county and has been bailed to a date in late May, Scotland Yard said.
Telecoms firm TalkTalk said it was the target of a cyber attack on October 21 last year in which the personal details, bank account numbers and sort codes of thousands of customers were accessed.
The five other people arrested in relation to the alleged theft of data includes a 15-year-old boy from County Antrim, Northern Ireland.
He was arrested on suspicion of Computer Misuse Act offences on October 26 2015, taken into custody at a County Antrim police station and bailed to return pending further inquiries.
A 16-year-old boy was arrested at an address in Feltham on October 29 and is currently on bail until a date in early May.
Detectives arrested a 20-year-old man in Staffordshire on October 31. He returned on bail on April 20 and has been re-bailed to mid-June.
On November 3, a 16-year-old boy was arrested in Norwich and is currently on bail until early May.
An 18-year-old man was arrested in Llanelli, Wales, on November 24 on suspicion of blackmail. He is on bail until mid-June.