The 37-year-old had never used a smartphone and didn't realise the danger her son was in, until she received a $500 bill and faced some "scary" questions from her boy.

"I was extremely shocked," Sabine says.

The mother-of-three discovered inappropriate games and in-app purchases last month, prompting her to speak out ahead of National Child Protection Week which runs September 1 to 7.

"I would watch him access the homework app on the iPad and I'd go away to cook dinner or tend to the other children, and he was left unsupervised," she told AAP.

Her comments come after research, published on Sunday, revealed two thirds (63 per cent) of parents fail to secure their devices with passwords, and one in two (55 per cent) allow their children unsupervised access online.

The survey of 2000 Australians over the age of 18, commissioned by child abuse prevention agency Act for Kids, also found two thirds (67 per cent) of parents to children under 12 feel they need more education on how to protect children from accessing inappropriate content.

Sex abuse educator Miranda Bain says there's a gap in awareness and knowledge among parents and educators who give children phones and other technology.

Unsupervised access could mean anything from handing a toddler a phone while you shower, to hours of time alone with a device.

"It's important we make the link between locking the back door and locking the phone or other smart devices," said the Act for Kids Program Manager.

Anything with a WiFi connection presents a danger, Ms Bain said.

One client, a teenage girl, managed to post on Twitter via a smart fridge after her parents had taken away the phone, she said.

Children, and their predators, are often more savvy than parents and every device - from baby monitor to smartphone - needs to be secured, she added.

Child protection expert and Bravehearts founder Hetty Johnston says offenders are chasing children through a dangerous online playground.

"Stranger danger is back," she told AAP.

"We are handing children devices loaded with porn. An offender may as well be sitting on the bed next to them, meanwhile we are sitting on the lounge watching television."

Many parents think their child is smart enough to avoid the bad content, or they are safe on kid-friendly apps, she said.

"Have a very open dialogue with your kids... Silence, secrecy, shame and fear are the offender's best friends," she said.

Australian Associated Press