Online social networking has grown more than 35% in Europe over the past year. About 42 million people are regular users, a number expected to more than double by 2012.

Social networking sites encourage users to feel that they're among a close set of friends when in fact there could be millions of people reading about them. These digital warehouses of private information raise the risks a user will receive harassing messages or be approached by a sexual predator.

They are also a goldmine for online advertisers, because users post information about themselves and can then be targeted with products and services likely to appeal to them.

Under a deal signed during  a ceremony marking Safer Internet Day, the 17 companies agreed to ensure that:

• users can report abuse with a single click
• the default setting for online profiles and contact lists is set to “private” for users under 18
• private profiles of users under 18 will no longer be searchable
• privacy options will be more prominent so users know who can see what they’ve posted online - only their friends or the whole world.

The companies promised significant progress towards implementing the agreement by April 2009. In some cases the policies have already been put in place as networks try to protect themselves against claims of privacy violation and illegal activity. MySpace has purged 90 000 sex offenders over the past two years.

Viviane Reding, the commissioner for information society and the media, called the agreement an “important step” in making social networking safer for children.

The commission has also launched a campaign against cyber-bullying – harassment via the web or mobile phone. A growing problem, this typically takes the form of hostile text messages or photos or videos posted to embarrass users.

As part of the campaign, a video clip about a young girl being targeted by cyber-bullies is airing on public and private TV channels across Europe.