With a campaign looking into online bullying being launched, we look at five celebrities who have been the victims of web trolls.
Take That star Gary Barlow received offensive tweets about his late daughter Poppy, who was delivered stillborn last August.
An account believed to belong to former Big Brother contestant Kenneth Tong tweeted song lyrics from the band to mock Barlow and his wife.
X Factor judge Louis Walsh called the comments "vile" on his official Twitter account.
Olympian Tom Daley received a malicious tweet last July saying that he had "let his dad down."
The diver's father Rob died in 2011 after a long battle against brain cancer.
The 17-year-old boy who sent the tweet apologised through the social networking site and was issued with a harassment warning.
Caroline Flack found herself the target of Twitter trolls when she was dating One Direction's Harry Styles.
The television presenter contacted the police after one fan sent Flack a threatening picture of her holding a knife.
BBC Sport presenter Gary Lineker said he felt "physically sick" when a Twitter-user taunted his son George over his childhood leukaemia.
The user told George Lineker it was a "pity ya (sic) didn't die", referred to him as "leukaemia boy" and called Gary "washed up."
Lineker later accepted the apology from 21-year-old Mark Sinnott, saying he hoped the troll would "learn from his idiocy."
Former Blue Peter presenter Richard Bacon revealed he was the victim of online abuse from a number of anonymous internet trolls.
Bacon took matters to the police when the trolls started targeting his family members, including his mother, wife and baby son.
He said he wanted to track down and meet his trolls but was advised not to by the police.
- If you are affected by cyber bullying or bullying of any kind, contact ChildLine on 0800 1111 or go to their website www.childline.org.uk.