Facebook has partnered with security vendors Symantec, McAfee, Microsoft, Sophos, and Trend Micro in a program to improve Facebook's security and broaden the availability of the antivirus softwares.
Blacklisted URLs:
When a Facebook user posts a link to one of the blacklisted URL, Facebook pops up an interstitial warning page before the browser actually connects off to the suspicious destination. Facebook's partners in this effort included McAfee, Google, Web of Trust, and Websense. Facebook's URL blacklist system will now include the malicious URL databases of all of the security vendors.
Antivirus Marketplace:
Facebook launched its own Antivirus Marketplace, where users can download the various antivirus software packages from Microsoft, McAfee, Trend Micro, Sophos and Symantec under six-month free licenses. These companies will also be able to use the Facebook Security Blog to post their bulletins and information for its more than six million followers.
Facebook Antivirus Marketplace