The hackers of T-Mobile US got access to more account information than earlier estimated with the company saying hackers accessed personal information of an additional 5.3 million customers so that the total number of people affected is more than 53 million.
The company earlier informed that personal data of more than 40 million former and prospective customers was stolen together with data from 7.8 million existing T-Mobile wireless customers.
US Federal Communications Commission (FCC) has opened an investigation of the breach.
The data includes addresses, dates of birth and phone numbers of customers, the company said, adding that it had no indication that the accessed data contained financial information such as credit card or other payment data.
Information about the attack was first published at on online forum. The company said it has located and closed the access point that it believes was used to illegally gain entry to the servers.
“We have no indication that the data contained in the stolen files included any customer financial information, credit card information, debit or other payment information”, the company has said.