Nearly all of us now routinely use some form of online social network for staying in touch with friends, for sharing photos and even for developing business relationships. Social networking, through sites such as Facebook, Myspace and LinkedIn, is an internet phenomenon that seems to have unlimited growth potential.

Some people can’t leave it alone, even when they’re at work. And that facet of modern working life hasn’t gone unnoticed by cyber criminals.

Businesses are increasingly worried about being targeted by hackers through the medium of online social networks. Nearly three-quarters of firms are concerned that their workers’ behaviour on social networks is putting their business at risk, according to a survey by Sophos, the IT security and data protection firm.

Sophos’s survey revealed that criminals increasingly focused attacks on social networking users in 2009, with an explosion in the reports of spam and malware: 57% of users reported they had been spammed via social networking sites, a rise of 70.6% from 2008; 36% said they have been sent malware via social networking sites, a rise of 69.8% from last year.

Sophos surveyed over 500 organizations, and discovered that 72% are concerned that employee behaviour on social networking sites exposes their businesses to danger, and puts corporate infrastructure - and the sensitive data stored upon it - at risk.

Survey respondents were asked which social network they believed posed the biggest security risk, with 60% naming Facebook; 18% said MySpace; 17%, Twitter, and; 4% LinkedIn.

Social networks have become very popular with criminals as a way of spreading malware, Rik Ferguson, Senior Security Advisor at internet security specialists Trend Micro, confirms: “So much so, that some kinds of malware, such as the widespread Koobface, have been developed specifically to take advantage of the phenomenon.

“Information theft, spamming, exploitation of software vulnerabilities, social engineering - all of these are now commonplace events on social networks,”