Web bullies target children in their homes
They offer instant communication and the feeling of being connected to hundreds of "friends".
But social networking websites are being used by children and teenagers to bully each other on a disturbing scale, new research has warned.
Not only are they "posting" hostile and threatening messages, some are even using the technology to send anonymous abusive messages.
A new study to be published this week will show that "cyber-bullying" has now affected a third of teenagers, with many feeling unable to tell parents or teachers about their experience.
This week charities will use a conference in London to call for social networking websites to stop bullies sending messages anonymously, saying that it is particularly damaging to children and teenagers.
The practice, known as "trolling", has been linked to self-harm among victims and even, in the most extreme cases, suicide.
They will say that new websites which make use of Facebook - by far the most popular social networking medium - are encouraging the anonymous posting by making it easy and accessible to under-18s.
The report, by charity the Diana Award, is the biggest study yet of cyber-bullying.
It questioned 1,512 young people aged 11 to 16 across England and found that 38 per cent had suffered abuse online, and that 28 per cent of victims have not told anyone about their experience.
Nearly half of youngsters feel current attempts to prevent online bullying are inadequate.
The report also found that older teenagers are at a greater risk of cyberbullying and are exposed to more aggressive forms of behaviour, such as death threats and explicit images.
The survey will be published as part of national anti-bullying week, which comes after the daughter of Meera Syal, the actress, spoke of the cyber-bullying she suffered when she was accused of "glassing" another pupil at her private school, a charge of which she was cleared.
The lack of regulation of the internet was highlighted last night as Joanna Shields, the head of Facebook in Britain, admitted she had allowed her son onto the site despite being 12, one year under its minimum age.
Last night she closed his account and said: "It was only after much discussion, agreeing to monitor my son online and knowing he was protected by privacy settings we have designed for minors, that I took the decision to allow him to use Facebook.
"However, despite this careful consideration as a family, I am by no means exempt from the rules that govern Facebook and per our policies, the profile has been removed from the site."
Miss Shields is also a trustee of the Save the Children Fund and on a fund-raising board for the National Society for the Prevention of Cruelty to Children, both of whom campaign against bullying.
Beatbullying, the charity endorsed by the Duchess of Cambridge and Prince William as an official recipient of money raised from their wedding, said it was particularly concerned about the growth of "trolling".
One website, Formspring, has been particularly linked to anonymous cyberbullying.
In one of the most disturbing incidents Natasha MacBryde, a 15-year-old from Bromsgrove, in the West Midlands, killed herself in February this year after repeated bullying, including being sent a number of anonymous messages on Formspring.
Her parents, Andrew and Jane MacBryde, said they believed these had played a significant role in the events leading up to her death.
Formspring allows its 25 million members to send unmoderated questions or messages to each other anonymously. Many are drawn into it through Facebook, which itself prevents anonymous messages.
The introduction can work when a Facebook user sees an invitation from a Facebook friend to ask a question.
With one click, they find themselves invited to join Formspring and to send invitations to their Facebook friends, creating a "viral" effect.
Victims of cyberbullying have said their tormentors used Formspring to launch vicious character assassinations and post hurtful personal comments.
One 17-year-old girl who suffered weeks of abuse said: "Because they were anonymous they thought they could get away with it. Fewer people would bully online if they had to put their names to it."
Richard Piggin, the deputy chief executive of the children's charity Beatbullying, said: "Users should not have the option of remaining anonymous on sites such as Formspring and other social networking platforms.
"Anonymity encourages people to act in a way they might well not in real life or if they were named online."
He added: "Whatever sites like Formspring say about anonymity allowing people to express themselves, it is clear that it is being used in a negative way by allowing children to hide behind it in order to abuse others.
"Other social networking sites encourage you to use your real identity, which is a positive thing. Formspring needs to make changes."
Ending anonymity is one of a series of reforms charities now want from the websites.
Very few laws govern behaviour on the internet, and it is extremely difficult for police to trace anonymous postings, as the websites which allow them are almost all registered abroad.
Charities want internet and mobile phone networks to provide stronger safeguards against bullying, including better safety features, more regulation and codes of conduct.
They are particularly concerned about how difficult bullying victims find reporting abuse to social networking sites and say that "takedown times" - the speed with which abusive messages are removed must be improved.
Professor Mary Kellett, director of the Open University's Children's Research Centre and co-author of the Diana Award's report, said: "This youth-led report demonstrates the impact that cyberbullying is having on young people's lives, the pace at which it reinvents itself and the inadequacy of current measures to contain it.
"This is no longer an acceptable situation. Politicians and childhood professionals, entrusted with the guardianship of our young people, must take note of its findings and take some bold steps to tackle the issues."
Emma Jane Cross, chief executive of Beatbullying, said: "Bullying and cyberbullying is at epidemic levels.
"Teachers, parents, Government, charities, internet service providers and police must all come together to take the necessary steps required to stop bullying in schools, the wider community and online environment, so that online takedown times are reduced and reporting mechanisms are both accessible and functional."
Formspring is headed by Ade Olonoh, a computer science graduate, who has raised around £8.5 million from a group of venture capitalists who previously made money from investments in Twitter and other internet success stories.
Asked recently in America about bullying on the site and reports that a user in the United Sates had committed suicide after being taunted, Mr Olonoh denied that Formspring lent itself to abuse and complained about the negative way the site was being portrayed.
A spokesman for Facebook said: "Nothing is more important to us than the safety of the people that use our service.
"Unlike other websites and forums Facebook has a real name culture, which provides greater accountability and a safer and more trusted environment.
"We are clear that there is no place for bullying or harassment on Facebook and we respond aggressively to reports of potential abuse.
"We provide our users with the tools to report abuse on every page and the option to block people from having any further contact with them.
"Reports involving bullying are prioritised, reviewed by a trained team of reviewers and removed if they violate our terms.
"Formspring is a separate company - it is not connected to Facebook and we have no partnership with them."