2. Acxiom

Date: Aug. 8, 2003

Impact: 1.6 billion customer records hacked

A hack initiated by Scott Levine broke into Axciom network and over 1.6 billion customer records were stolen and 8.2 gigabytes of personal data had been downloaded with the span of a year. The incident caused a $7 million of damage and Scott was sentenced eight years in prison.

1. Epsilon

Date: March 30, 2011

Impact: To Be Determined

The names and e-mails of customers that were stored in over 108 retail stores, plus several huge financial firms like CitiGroup Inc. and the non-profit educational organization, College Board, were exposed after an unknown attacker hacked into Epsilon's systems. The estimated loss incurred by epslon is about $4 Billion.