A growing number of UK firms are banning their employees from using social networking sites at work, partly because of IT security concerns, a new report has found.

The study, conducted by MessageLab, found that almost 20 per cent of companies now restrict access to site such as Facebook and MySpace.

Paul Wood, security analyst with MessageLabs, explained that while it is not always obvious, such sites can present an IT security risk for companies if employees are lured on to pages containing malicious code.

He said: "Organisations need to raise awareness about the risks of these sites. Some of the policies are not up-to-date."

Mr Wood added that firms should make sure they update their IT security and usage rules in light of the services offered by newer Web 2.0 sites.

This week, ITPro reported that a Sophos study had found that two-thirds of business computers are not adequately protected against IT security threats.

According to a recent survey by Connect, the two biggest IT headaches for businesses were 'everyday hassles with IT' (37 per cent) and 'security concerns' (32 per cent) In a recent survey of SMEs for Connect, the two most important benefits of outsourcing were 'guaranteed response times' and 'allowing in-house IT staff to concentrate on more strategic issues'