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Panorama's Declan Lawn reports on the dangers of cyberbullying and meets pop singer Cher Lloyd, who has experienced racist attacks and physical threats on social networking sites.

He also tracks and confronts a man known to troll the internet and post offensive comments on tribute pages on social networking sites.

Panorama: Hunting the Internet Bullies, BBC One, Monday, 6 February at 20:30 GMT and then available in the UK on the BBC iPlayer.