* Customer names, e-mail addresses exposed
* Large Epsilon data breach widens to many U.S. customers
NEW YORK, April 3 (Reuters) - Citigroup Inc (C.N) and Capital One Financial Corp (COF.N) were part of a large data breach that exposed the names and e-mail addresses of many large companies' customers, including those at some of the nation's largest banks.
The online marketer Epsilon, a unit of Alliance Data Systems Corp (ADS.N), said on Friday that a person outside the company hacked into some of its clients' customer files. The vendor sends more than 40 billion e-mail ads and offers annually, usually to people who register for a company's website or give their e-mail addresses while shopping.
Citigroup customer names and some credit card customers' e-mail addresses -- but no account information -- were exposed as part of the data breach, the third-largest U.S. bank said on Saturday.
Capital One also said the Epsilon hacker accessed its customer e-mail addresses, but no personally identifiable information.
JPMorgan Chase & Co (JPM.N), the second-largest U.S. bank, and Kroger Co (KR.N), the biggest U.S. supermarket operator, said on Friday that some customers had their names and e-mail addresses exposed as part of the data breach. [ID:nL3E7F13F4]
Citigroup announced that it had been affected on Saturday evening. Spokesman Sean Kevelighan said the bank started informing its customers of the breach on Friday through a link on its website. (Reporting by Maria Aspan, additional reporting by Jonathan Spicer, editing by Maureen Bavdek)