Epsilon sends 40 billion e-mail ads and offers annually, usually to people who register for a company's website or who give their e-mail addresses while shopping

Epsilon, said AbeBooks, has advised us that the files that were accessed did not include any customer information other than email addresses.

As a reminder, AbeBooks will never ask customers for personal or account information in an e-mail. Please exercise caution if you get any emails that ask for personal information or direct you to a site where you are asked to provide personal information.

In what could be one of the biggest such breaches in US history, a diverse swath of companies that did business with Epsilon stepped forward over the weekend to warn customers some of their electronic information could have been exposed report Reuters.

Drugstore Walgreen, Video recorder TiVo Inc, credit card lender Capital One Financial Corp and teleshopping company HSN Inc all added their names to a list of targets that also includes some of the nation's largest banks.

JPMorgan Chase & Co, the second-largest U.S. bank, and Kroger Co, the biggest U.S. supermarket operator, said that some customers were exposed as part of the Epsilon data breach.

Citigroup announced that it had been affected Saturday evening. Some of Epsilon's other clients include Verizon Communications Inc, Blackstone Group LP's Hilton Hotels, Kraft Foods Inc, and AstraZeneca.