To protect its 900 million plus users from online attacks, Facebook has formed an alliance with five security vendors to protect its members\' data as the social networking site has become a fertile breeding ground for hoaxes, spam and chain letters. Microsoft, McAfee, TrendMicro, Sophos and Symantec have agreed to share their URL blacklists with Facebook in an effort to combat malware. The new Facebook Anti-virus Marketplace offers free six-month licences from the security vendors for PCs and Macs. The URL blacklist system, which scans trillions of clicks per day, will now incorporate malicious URL databases from these security companies to augment existing level of protection. According to Facebook, spam makes up less than four per cent of the content shared on its pages. Facebook will inform users if the link they clicked on is malicious, and users will be sent to a page that offers the choice to continue at their own risk, return to the previous screen, or obtain more information on why the link was flagged as suspicious. According to Websense Security Labs, a US-based company specialising in web filtering software, around 55 per cent of data-stealing malware communications are on the internet while 82 per cent of malicious websites are hosted on compromised hosts. Charles Renert, vice-president of Websense, said that around 43 per cent of activities on Facebook are streaming media, which is more than five times the next largest category of news and media within Facebook.