Ryan Halligan was taunted for months. Classmates spread rumours via instant messaging that the 13- year-old boy was gay. A popular female classmate pretended to like him and chatted with him online, only to copy their exchanges to her friends. Unable to cope, the teenager from Vermont in the US killed himself.

Gail Jones, a 15-year-old Briton, took her life after receiving, at one point, 20 silent calls on her mobile phone every 30 minutes. Her father, Glyn, suspects a final call in the middle of the night pushed her over the edge.

These are extreme but far from unique examples of the devastation wrought by cyber bullying. Internet usage by children has increased enormously since Halligan died in 2003 and Jones in 2000, so it's likely that online bullying - which includes sending threatening messages, displaying private messages and posting embarrassing video footage and photos on the internet - is also increasing.

A 2007 study by the US-based Pew Internet & American Life Project found that one-third of American teen internet users have been targets of cyber bullies. And as online communication evolves from chatrooms and instant messaging to social networking, the venues where bullying occurs are becoming more central to young people's lives - and more public.
Research into cyber bullying is still in its infancy. But it is becoming clear that aspects of online communication encourage people to act aggressively, prompting them to do things...