Social networking site Facebook has introducing an automated service, to keep its users' accounts safe. Facebook created the service which monitors the web for stolen email addresses and passwords.
The service checks credentials to see if they match and correct to those being used on Facebook.
If it finds a set of stolen credentials, it passes the data into a program that analyses it in computer language.
Then the automated system checks it against the Facebook database to see if any of the email addresses and hashed passwords match login information on Facebook.
Facebook's security engineer Chris Long wrote in a blog post, "Theft of personal data like email addresses and passwords can have larger consequences because people often use the same password on multiple websites."
"We built a system dedicated to further securing people's Facebook accounts by actively looking for these public postings, analyzing them and then notifying people when we discover that their credentials have shown up elsewhere on the Internet," he added.
The report said that if it finds a match, Facebook notifies the affected user the next time they log in and guides them through a process to change their password.