When it first caught on, social networking was seen as little more than an irritation for employers and an employee time waster.

But a report from security firm Sophos has indicated that social networking has the potential to do a lot more damage, with a 70% rise in the number of firms that report spam and malware attacks via social networks during 2009.

According to Cisco, almost 2% of all online clicks in 2009 through 4,000 Cisco web security appliances have been on social networking sites, 1.35% on Facebook alone.

A Sophos survey attached to the report, conducted in December 2009, revealed that 60% of respondents believe that Facebook presents the biggest security risk of the social networking sites, significantly ahead of MySpace, Twitter and LinkedIn.

“With individuals and businesses hooked on online social outlets, cybercriminals have taken notice and started using them for their gain. Beyond the common nuisances, such as wasted company time and bandwidth, malware and malicious data theft issues have presented serious problems to social networks and their users. Spam is now common on social networking sites, and social engineering—trying to trick users to reveal vital data, or persuading people to visit dangerous web links—is on the rise,” explained the report.