There has been a massive rise in spammers and hackers hunting for victims at online social networks, an explosion of spam messages and nefarious software targeting users of sites like Facebook and Twitter.

A report by data protection firm Sophos found 57% of online social network users reported getting spam in their virtual communities. That amounted to a 70.6 percent jump from the prior year. About 36% of social network users said they had been sent software worms, viruses or other types of "malware". That's up 69.8% from the previous 12-month period.

By far, the ones most at risk were on Facebook which makes sense. It is the biggest one and it's hard to vet 350 million users.

The report also found that 49% of companies allowed their employees access to social networking sites. Given the potential for damage to corporate infrastructure, not to mention out and out theft, you would have to say it's a matter of time until corporations start bringing in stricter rules.

Graham Cluley, senior technology consultant for Sophos warns that companies might be playing with fire. Cluley says: "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. 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."

Other security experts have warned that online sites are havens for online criminal activities. What happens now is that user's accounts are hijacked, usually by sending out some sleazy invite, and messages containing malware are sent to everyone who is "connected" to the sender.

Now, most corporations will probably ban the use of social networking sites but that's unlikely to help. Besides, social networking sites do provide some value and connections. A better alternative would be to educate users about the risks.