As more organizations allow employees to use social media like Facebook and Twitter at work, cybercrime attacks on these networks have exploded, according to a report released Monday by IT security firm Sophos. Reports of malware and spam rose 70 percent on social networks in the last 12 months, the security survey revealsSophos' investigation, titled "Social Security," finds 57 percent of users report they have been spammed via social networking sites, and 36 percent reveal they have been sent malware via social networking sites. The "Social Security" survey is part of Sophos' 2010 Security Threat Report, which looks at current and emerging computer security trends. Read about some of most common ways users get taken on social networks in 5 Facebook, Twitter Scams to Avoid and 5 More Facebook, Twitter Scams to Avoid"Computer users are spending more time on social networks, sharing sensitive and valuable personal information, and hackers have sniffed out where the money is to be made," said Graham Cluley, senior technology consultant for Sophos. "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."While most of the 500 firms Sophos polled, 72 percent, were worried workers behavior on social networks is putting their business at risk, almost half of them, 49 percent, allow all of their staff unfettered access to Facebook and other social networking sites. (See also: Facebook, Twitter, LinkedIn: Security Pros Warm to Web 2.0 Access)"The grim irony is that just as companies are loosening their attitude to staff activity on social networks, the threat of malware, spam, phishing and identity theft on Facebook is increasing," said Cluley.Survey respondents were also asked which social network they believed posed the biggest security risk and 60 percent said Facebook."We shouldn't forget that Facebook is by far the largest social network - and you'll find more bad apples in the biggest orchard," explained Cluley. "The truth is that the security team at Facebook works hard to counter threats on their site - it's just that policing 350 million users can't be an easy job for anyone. But there is no doubt that simple changes could make Facebook users safer. For instance, when Facebook rolled-out its new recommended privacy settings late last year, it was a backwards step, encouraging many users to share their information with everybody on the internet."The report also points out the inherent security problems presented by LinkedIn, which is a social network targeted to working people that allows them to network and job seek, among other things. Although LinkedIn is considered to be by far the least threatening of the networks, Sophos advises that it can still provide a sizeable pool of information for hackers."Targeted attacks against companies are in the news at the moment, and the more information a criminal can get about your organization's structure, the easier for them to send a poisoned attachment to precisely the person whose computer they want to break into," explained Cluley. "Sites like LinkedIn provide hackers with what is effectively a corporate directory, listing your staff's names and positions. This makes it child's play to reverse-engineer the email addresses of potential victims."