A new study of U.S. teenagers' behaviour online suggests that most of them take measures to protect their personal information on social networking sites like Facebook and MySpace.

The survey by the Pew Internet and American Life Project, released Wednesday afternoon, also suggests that in spite of security measures that are available to teens online, they still face personal risks associated with internet-based communications.

In a scientific survey of 935 young people aged 12 through 17 conducted over four weeks in October and November 2006, 53 per cent of respondents said they have online profiles, two-thirds (66 per cent) of whom said they limit access to the information and that it is not visible to all internet users.

Some 46 per cent of those who said their profiles are available to anyone online stated that they provide false information in their profiles as a means to protect themselves or play a joke.

About 91 per cent of teens on social networks say they use the systems to keep in touch with people they know or see frequently, and 82 per cent use the services to maintain contact with friends they don't see often.

Nearly half, or 49 per cent, said they use the social networks to make new friends.

Almost a third of all online teenagers — 32 per cent — said they have been contacted by strangers over the internet, although that contact was not exclusively through social networking sites.

Some seven per cent of teens all teens online, or 21 per cent of those who had been contacted by strangers said they have entered a conversation with those individuals in a bid to find out more about the person who was contacting them.

A similar number said they felt scared or uncomfortable as a result of online encounters with strangers — seven per cent of online teens, or 23 per cent of all of the group that had been contacted by strangers.