An unauthorized person stole names, addresses and possibly credit card data belonging to 77 million account holders on Sony's PlayStation Network in what could be one of the largest-ever Internet security breaches.
Internet security experts believe that these systems were breached by hackers who persuaded unsuspecting system administrators to load malicious software onto their machines. Here are some other large Internet security breaches:
April 2011 -- Online marketer Epsilon, which sends billions of emails a year for clients that represent a "Who's Who" of major banks and retailers, reports a breach of its system. It says that some clients' customer names and email addresses were stolen.
2010 -- Security researchers identify a computer worm dubbed Stuxnet that they speculate was designed to breach a system used to refine uranium in Iran at that nation's Natanz enrichment plant.
2010 -- Google Inc says that it was the victim of a cyber attack on its operations in China that resulted in the theft of its intellectual property. Google said that the networks of more than 20 other companies had been infiltrated.
2009 -- Hacker Albert Gonzalez pleads guilty to stealing tens of millions of payment card numbers by breaking into corporate computer systems from businesses including payment card processor Heartland Payment Systems, TJX Company Inc, 7-Eleven Inc and Target Co