The popularity of Facebook and other social networks is accompanied by an alarming rise in attacks on users of those websites, according to a report published Monday by computer security firm Sophos. '2009 saw Facebook, Twitter and other social networking sites solidify their position at the heart of many users' daily Internet activities, and saw these websites become a primary target for hackers,' Sophos said in its 2010 Security Threat Report. The report found that cybercriminals have increasingly focused attacks on social networking users in the last 12 months, with 57 percent of users said they had been spammed via social networking sites, a rise of almost 71 percent from last year. Nearly 36 percent of users surveyed also revealed that they had been sent malware via social networking sites, an increase of about 70 percent compared with the previous year. 'The dramatic rise in attacks in the last year tells us that social networks and their millions of users have to do more to protect themselves from organized cybercrime, or risk falling prey to identity theft schemes, scams, and malware attacks,' Graham Cluley, senior technology consultant for Sophos, said in a statement. Many Web 2.0 sites are concentrating too much on growing their market share at the expense of properly defending their existing users from Internet threats, Sophos noted in the report. 