(ShareCast News) - A fourth person has been arrested in connection with the TalkTalk cyber attack.The Metropolitan Police said a 16-year old boy was arrested at an address in Norwich on Tuesday evening on suspicion of Computer Misuse Act offences.The boy has been bailed pending further enquiries to a date in late March next year.On Saturday, a 20-year old man from Staffordshire was arrested. This followed the arrest of a 16-year old boy in Feltham last Thursday and a 15-year old boy in Country Antrim, North Ireland, last Monday.They have all been released on bail pending further enquiries.TalkTalk said last Friday that the extent of the data accessed in the cyber attack was significantly less than originally suspected.The company said fewer than 21,000 unique bank account numbers and sort codes and 28,000 obscured credit and debit card details were accessed.In addition, it said fewer than 15,000 customer dates of birth and 1.2m customer emails addresses, names and phone numbers were accessed.TalkTalk said that as previously confirmed, the credit and debit card details cannot be used for financial transactions.