Dropbox is a cloud-based data storage company which told on Thursday that passwords and user IDs of its around 68 million customers are recently leaked on internet while they were stolen four years ago. The company told that it has no clue about wrong entry of any of its user account while it has already informed the users about this incident and instructed them to change their passwords on their accounts.

Just two weeks before the online posting of these accounts, the company could know about this incident but it doesn’t know how it happened and who is behind this hacking. It told in an email that email addresses and passwords present on the online data are real and they apologized for the whole incident.

Dropbox thinks that this happened in 2012 and they emailed all the customers to change their password if they hadn’t change their password since mid-2012 after knowing about this problem. They ensured that these passwords can’t be used to access Dropbox accounts even if they are hacked.

The company also told its users to change their password of Dropbox on other services if they signed up before 2012 in order to protect the other account as well. It added that email addresses were also included in the list due to which users should remain alert for phishing or spam.

Earlier this year, Dropbox told that it has more than 500 million users that store and share pictures, videos and business files etc. on its cloud servers.