Slideshow: 15 worst data breaches

RSA

Impact: Possibly 40 million employee records stolen. The impact of the cyber attack that stole information on the company's SecurID authentication tokens is still being debated. The company said two separate hacker groups worked in collaboration with a foreign government to launch a series of spear phishing attacks against RSA employees, posing as people the employees trusted, to penetrate the company's network. EMC reported last July that it had spent at least $66 million on remediation.