Users can select three to five trusted contacts from their security settings at any time. These contacts should be available via phone or in person.
This feature could be helpful when a user suffers a mass compromise, meaning he or she loses access both to email and other accounts as a direct result of malware infestation. However, these cases are rare, and most users lose access only to specific accounts in targeted phishing schemes.
How it works:
Once users go into their Facebook Security Settings and select three to five people as trusted contacts, Facebook notifies those people.
When users can't log into their Facebook accounts, they can turn to their trusted contacts for help. Each contact will get a security code with instructions on how to use it. Users need security codes from three trusted contacts to recover their Facebook accounts.
When there's a problem, Facebook will generate an URL dynamically and the user's trusted contacts go into their own personal security settings and find the URL. The URL will give the contact a code and instructions on what to do with it.
Source: Tech News World