Spammers have turned their attention to Twitter and Facebook and the US is leading the list of shame.

That's according to security company Sophos which stated in its recent report that cybercriminals have shown an increased attraction to social networking sites like Facebook and Twitter during this last quarter,  a sign that spammers are successfully adapting their methods to suit the current environment.

These sites have become part of many computer users' daily routine - whether it's logging on to see what their friends are up to, viewing photos, or updating their status, masses of personal information is updated every minute. Such frequent use makes social networking sites a prime target for spammers and malware authors who typically attempt to break into innocent users' accounts and take advantage of trusted social networks to send spam and malware.

For example, in November, Sophos reported that Facebook had won a US$873 million judgment against a Canadian man who bombarded millions of Facebook members with unsolicited spam messages. The spammer tricked users into revealing their passwords and usernames and then used the information to gain access to their personal profiles. Facebook claimed that the man then sent out more than four million messages promoting products from marijuana to sexual enhancement drugs.

"Cybercriminals have cottoned onto the fact that social networking users can be more easily fooled into clicking on a link that appears to have come from a trusted Facebook friend, than if it arrived as an unsolicited email in their inbox," said Graham Cluley, senior technology consultant at Sophos. "The notorious Nigerian 419 scammers have even evolved, masquerading as Facebook friends in order to trick unwary users into parting with valuable sensitive and financial information. Ultimately while users are still falling for these scams, the fraudsters will continue. And while the authorities are making great progress, everyone must take steps to ensure they don't fall victim."

Sophos also revealed the top twelve spam-relaying countries for the final quarter of 2008. Between October and December 2008, the US relayed most of the world's unwanted emails. China has leapt back into second place, relaying a larger proportion of spam than it did in 2004, and Russia retains third position. In contrast, other nations like Canada, Japan and France - serial offenders five years ago - appear to have made progress and are no longer present in the list of spam reprobates.

"Although there's no denying that some countries have significantly reduced their contribution to the spam epidemic over the past five years, the US still holds the crown," said Cluley. "Though its spam contribution has significantly decreased since Bill Gates's 2004 prediction (that spam would be a thing of the past in five years' time) - falling from almost half of all spam relayed at the end of 2004, to 21.3 percent by the end of 2007, and now resting at 19.8 percent - this shows there's certainly no quick fix."