TalkTalk hack: bank account details of 21,000 customers and names and addresses of 1.2 million were affected

Another 28,000 obscured credit and debit cards were also accessed as well as 1.2 million customer email addresses

(AFP/Getty Images)

TalkTalk has confirmed the number of customers whose data was hacked in a cyber attack as 21,000.

Another 28,000 obscured credit and debit cards were also accessed as well as 1.2 million customer email addresses, names and phone numbers, the company has said.

TalkTalk made the announcement as a second teenage boy was arrested in connection with the attack. The second arrest was made in Feltham, London on the grounds of suspicion of Computer Misuse Act offences. Officers also searched an address in Liverpool.

A teenage boy was arrested in County Antrim, Northern Ireland, on October 26. Both teenagers have now been bailed.

TalkTalk said that the scale of the security breach was significantly less than originally suspected. It had been able to say how many of TalkTalk's 4 million customers might be affected when news of the hack broke.

“Even though the scale of the attack is significantly smaller than initially suspected, we continue to advise customers to be vigilant, and to take all precautions possible to protect themselves from scam phone calls and emails," a spokesman said.