Many children are meeting up with people they first encountered on the internet - and their parents know nothing about it, a study claims.
Children often surf the net behind their parents' backs, research says
Web security firm Garlik surveyed hundreds of eight to 15-year-olds and found 20% have met an online friend in person - and one-in-20 do so regularly.
Just 7% of parents were aware of their child's behaviour, the study suggested.
Garlik, which advises people about data protection on the web, said youngsters were putting themselves in danger.
The firm polled 500 young people about their online habits - and 500 parents were asked about their attitudes.
It found that 40% of children regularly visit websites that are specifically prohibited by their parents and many give out sensitive information without parental consent.
Details divulged include full name (30%), home address (12%), school details (46%) and family photos (9%).
One in 10 admitted to being cyber-bullied - but only half said they had spoken to their parents about the ordeal.
Despite 90% of parents saying they monitored their offspring's internet usage, more than half of the youngsters admitted to surfing the internet when their parents did not know.
Garlik boss Tom Ilube labelled the research a "shocking wake-up call" to British parents.
"The web is a wonderful place to explore - but young people continue to make themselves vulnerable by not applying the same caution online as they would in person."