LinkedIn users might want to consider changing their passwords today.
The Mountain View-based social network for professionals says it is investigating reports that the passwords of more than six million users were stolen and leaked on the Internet.
Internet security firm Sophos says a file containing 6,458,020 passwords was posted on the Internet and hackers are working to try and crack them.
The company said it has also confirmed that the file contains at least some LinkedIn passwords.
"As such, it would seem sensible to suggest to all LinkedIn users that they change their passwords as soon as possible as a precautionary step," Graham Cluley of Sophos wrote in a statement. "Of course, make sure that the password you use is unique (in other words, not used on any other websites), and hard to crack."
Cluley also recommends LinkedIn members who use the same password to log into the social network as other sites, to also change the password for those other sites.
LinkedIn users can change their passwords by logging into their profiles and then clicking on their name in the top right corner and selecting settings.