4. Play Station Network

Date: April 20, 2011

Impact: 77 million Playstation Network accounts hacked 

Sony took responsibility of having conceded the biggest security breach of all times in which over 77 million accounts were hacked exposing millions of account ids and passwords including thousands of credit card details. All this while we thought the launch of PS3 was the worst thing that happened to Sony.

3. Heartland Payment Systems

Date: March 2008

Impact: 134 million credit cards exposed

Hackers monitored transactions of credit card accounts by running an SQL injection on the HPS site. They stole more than 134 million card details along with login ids and passwords.  Heartland discovered two Russian intruders were scanning its corporate network a few months after the breach started.