CardSystems Solutions
 CardSystems Solutions
Date: June 2005
Affected: 40 million
When hackers tapped into the servers of CardSystems Solutions, they made off with over 40 million Visa and Mastercard names, account numbers, and verification numbers. It wasn't very hard since CardSystems hadn't bothered to encrypt most of that data. Just months later,the company was acquired by Pay By Touch, a now-defunct payments company.

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