Teachers must protect children from cyber-bullying and other online threats encountered on social networks, an IT security firm has warned.

Secure Computing advised teachers that they could soon see more bullying in the virtual world than in the playground.

Social networking sites such as MySpace, which are hugely popular with teenagers, could also expose children to other risks. 

Schools need to be aware of the legal implications of their students accessing such sites, the company said.

"Within schools, social networking sites like MySpace put schools at risk from the legal liabilities of kids posting threatening or defamatory information about their classmates or their teachers," said Paul Henry, vice president of strategic accounts at Secure Computing.

"These networking sites have allowed kids to take threatening behaviour to the next level, basically allowing kids to become cyber-bullies from the comfort of their own home or from a computer in the school lab."

Accessing social networks also exposes children to security risks such as spyware, viruses, inappropriate content and the exposing of potentially revealing personal information that could be used for ID theft.

"It is important to educate kids about the dangers of networking sites," said Henry.

To minimise the risk, Secure Computing suggested that pupils should never post information that would make it easy for them to be located, such as phone number, postcode, school name or sports team.

Children should be urged never to add strangers to their friends list or to meet people they do not already know. If someone thought to be known starts to make inappropriate comments, they should alert a trusted adult immediately.