Massive breach exposes millions of e-mails.

• Position: CYBERCRIME - Brief article

In what may be the largest U.S. data breach to date, hackers gained access to the client files of online marketing provider Epsilon in April. Those files contained customer information supplied by many large U.S. retailers and banks, including Best Buy, Walgreens, Citigroup, and JPMorgan Chase.

Epsilon reported that the breach of its computer system exposed about 2% of its 2,500 corporate clients' customer information. Epsilon is a leading marketing services firm that sends more than 40 billion e-mails annually and has more than 2,500 clients, including seven of the Fortune 10, according to CBS News.

The good news for consumers is that no personally identifiable information (e.g., account or credit card information) was accessed. In a statement, Epsilon said, "The information...