They set up an account which would, to a child, seem to be an innocuous topic which they would see no reason not to “friend”. That then gives the paedophile access the child’s data, including pictures.

Maureen Griffin, a forensic psychologist and leading expert on social media safety, issued the warning and added that, as children have adapted so well on the dangers of stranger danger online, sex offenders have “come up with new and novel ways of gaining access to our children’s information”.

In a presentation for the Ennis Mental Health Association, Dr Griffin said she had, at primary school level, dealt with accounts set up pretending to be chicken nuggets and ice-cream in order to friend children.

She gave one “horrific” example where a sex offender here set up a fake social media account and posed as a road on which a girls’ secondary school was located.

“Over 400 girls at the school accepted ‘the road’ as a friend,” she said. “The owner of the account was a known convicted sex offender who made no effort to contact the girls, he didn’t follow them or meet them in real life or wait outside their school.

“He simply collected their photos, pictures from teenage discos, girls’ sleepovers, and a range of selfies.”

Dr Griffin, who has spoken to teachers, parents, boards of management and students at more than 700 schools here, along with making presentations to the gardaí and the HSE, said one of the best ways of protecting your children online is to make sure you know and trust their followers and friends.

She said adults with a sexual interest in children will take advantage of any site that is targeted towards children.

She gave the example of the site musical.ly.

“Musical.ly took off by storm here a year ago at primary school level,” she said. “It was a place where children could lip sync to their favourite songs and involves short little videos of the children dancing around singing their songs and posting the videos online.

“It is for 5, 6 and 7 year olds and I dealt with a case during the summer of a girl on musical.ly who had 20 followers — she did not know four of them. One of her followers told her that he would get her more likes for her songs if she sang her song again, this time in her underwear.”