Vodafone Germany said on Thursday it had been targeted in an attack on its data servers in which hackers gained access to the personal information of 2 million customers.
The person stole data including names,addresses, dates of birth, gender, sort codes and account numbers, the company said on its website. It added that the perpetrator did not have access to credit card information, passwords, PIN numbers, mobile phone numbers or data connections.
The attack was discovered by Vodafone and stopped. An individual had been identified by the police and their assets have been seized, the firm said.
Vodafone said it regretted the incident and was informing customers by letter. The telephone company's clients in other countries have not been affected, it said in a statement.
It warned that there was a heightened risk that customers could be the victim of a "phishing" attack under which criminals use personal information in a fake email to trick people into supplying further information online such as passwords or credit card numbers.