Date: March 2011
Affected: 60 million
As one of the world's largest permission-based e-mailmarketers, Epsilon helped clients like Best Buy, Capital One, and Walgreens send promotional emails to customers. Last April, the company was hit by a spear-phishing attack, which used fake, personalized emails to trick people into disclosing information such as passwords and financial details. In this case, an estimated 60 million customer emails from over 100clients were revealed.

JP Mangalindan, writer @FortuneMagazine - Last updated June 08 2012: 3:14 PM ET
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