Recently facebook team has pioneered with five antivirus software companies and provides users to a free and subscription-based antivirus packages called Facebook Anti-Virus Marketplace. Facebook has partnered with Microsoft, McAfee, TrendMicro, Sophos and Symantec.
Facebook also shared there URL blacklist system with these security vendors, so they can add it with their own URL blacklist database and provides very powerful security for 900 million facebook users.
You can download just one antivirus for each facebook account and some antivirus comes with a 6 months subscription.
The AV Marketplace enables people to download six-month licenses to full versions of anti-virus software at no charge from Microsoft, McAfee, TrendMicro, Sophos, or Symantec. Facebook’s global community can now download for free powerful software to protect their computers from current and future viruses, and content security threats providing hundreds of millions of people free access to anti-virus software.
Facebook’s Antivirus Marketplace is available to both windows and mac users.
You can download Free Antivirus from Facebook Security