Online bullying is rapidly growing in size and intensity. A new breed of self-styled "trolls" are stalking social networking websites, aiming their vicious attacks at victims who range from TV celebrities to grieving teenagers. Declan Lawn meets X... (more) Factor star Cher Lloyd, who describes how cyber attacks are ruining her life, and highlights a new survey revealing that one in thirteen young people face persistent online bullying. Panorama tracks down some of the bullies and asks: what more could be done to stop them?