Parents and teachers cannot keep up with technology quickly enough to effectively deal with cyber bullying, the Children's Commissioner has said.
Sally Holland said young people in Wales need "safe spaces" to talk about bullying on social media platforms.
Communications watchdog Ofcom recently reported that one in 10 young people aged 12-15 have been bullied online.
Advice service Get Safe Online said "the bully is in the back pocket" and cyber bullying happens "24/7".
Research by the UK Safer Internet Centre found 43% of young people knew someone who shared a photo or video of them without asking and a quarter also said they regularly shared screenshots of other peoples' photos.
Children's Commissioner for Wales, Sally Holland, spoke to more than 400 young people around the country along with 150 teachers and youth workers on the issue.
"We heard that children and young people have had enough of being told what to do and what not to do online, and want some space to talk about this complex issue in a safe atmosphere," she said.
"They also told us that adults around them, parents and teachers, don't understand their online world and can't keep up with the technology. That echoes what teachers and youth workers told us."
She has called on schools to create safe spaces for young people to talk and get support.
It is a story reflected by 15-year-old Rebecca, who was bullied after an innocent photo of her wearing a low-cut top at a party was shared on Snapchat by her boyfriend's ex.
"There were comments calling me things like sket and slag and other worse names," Rebecca, who is using a different name, told BBC Radio Wales' Eye on Wales programme.
"I froze and I was speechless. I didn't know what to think about it. It made me feel so bad about myself."
She added: "I felt really embarrassed because I hadn't had my say about it and there was no way I was going to get my say to about 300-plus people.
"It was just a photo that had been caught at the wrong time and at the wrong angle."
Liz Stanton, a family protection adviser for Get Safe Online, said: "When you look at bullying, people think of it as something that happens there and then in the playground.
"But when you look at online or cyber-bullying it's the hidden bullying that's going on. It's 24/7 every day. The bully is in the back pocket - where they're carrying the phone."
Jackie Doyle-Price, the UK government's suicide prevention minister, called on social media sites to "step up to the plate".
"We want social media not to be doing this through the stick of the law, we want them to do it because they want to look after their users," she said.
"Parents don't expect that their children are being exposed to risk when they are sitting in their bedrooms playing on their computers.
"But we need to do far more to educate children to protect themselves and make clear to them that this content will do them harm."
Eye On Wales: The bully is in the back pocket is available on BBC Sounds and will be aired on BBC Radio Wales on Wednesday, 6 February at 18:30 GMT.
For details of organisations which offer advice and support, visit bbc.co.uk/actionline