According to their Blog Post Note :
Our URL blacklist system, which scans trillions of clicks per day, will now incorporate the malicious URL databases from these security companies to augment our existing level of protection. This means that whenever you click a link on our site, you benefit not just from Facebook’s existing protections, but the ongoing vigilance of the world’s leading corporations involved in computer security.
Facebook also announced AV Marketplace. You can download the six-month license for a full version of anti-virus software for free. To download just go to AV Marketplace and download the Software for free.
They have 5 products McAFee , Microsoft Security Essentials , Norton Anti virus and Sophos Anti-Virus for Mac Home Edition. You are allowed to download only one of them.
Note: You can download this Anti-Virus only once.
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Don’t forget to like Facebook Security page to receive regular updates from them.