Thanks to the TrendMicro Blog for this informative article about social networking sites and their dangers:
Due to their ever-growing popularity, social networks have been a continuous target of cybercriminals to proliferate their malicious schemes. TrendLabsSM received samples of another Facebook spam, this time also taking advantage of the popular micro-blogging site, Twitter.
The mail, which poses as a Facebook notification message, uses adult-themed strings to lure users into opening the attachment. The .ZIP file attachment, Twitter.zip, contains the file twitter.html, which has an embedded malicious script that Trend Micro detects as JS_REDIR.AE.
Read more: http://blog.trendmicro.com/spammers-target-facebook-and-twitter-at-once/#ixzz0rahBsO7L