In June 2012 , cryptographic hashes of approximately 6.4 million LinkedIn user passwords were stolen by hackers who then published the stolen hashes online . This action is known as the 2012 LinkedIn hack . In response to the incident , LinkedIn asked its users to change their passwords . Security experts criticized LinkedIn for not salting their password file and for using a single iteration of SHA-1 . On May 31 , 2013 LinkedIn added two-factor authentication , an important security enhancement for preventing hackers from gaining access to accounts . In May 2016 , 117 million LinkedIn usernames and passwords were offered for sale online for the equivalent of $ 2,200 . These account details are believed to be sourced from the original 2012 LinkedIn hack , in which the number of user IDs stolen had been underestimated . To handle the large volume of emails sent to its users every day with notifications for messages , profile views , important happenings in their network , and other things , LinkedIn uses the Momentum email platform from Message Systems
2012 LinkedIn hack
2012 LinkedIn hack
LinkedIn