Recent phone scams have spurred several schools to warn parents of fake calls claiming their children have been kidnapped. And IT security experts have warned of the dangers of youngsters uploading their pictures to instant messaging apps.
In the past month, Hong Kong police have received at least three reports of attempts to abduct children. In one call, the criminals were able to give specific details of the child.
Good Hope Primary School and Victoria Shanghai Academy School are among the schools that have received reports of menacing phone scams, although no actual kidnappings have been reported so far.
"If a criminal tried to target one of those kids, he's now able to go to WhatsApp and download all this information. He knows exactly where that child is, what he or she looks like, because you're posting photos onto it," said Frank Yam, director of the international, non-profit Information Systems Audit and Control Association (ISACA).
Police advise social media users to be mindful of the privacy settings and make sure nothing is shared with unintended parties. They urge Android users to install anti-malware software.
It's not just smartphones that make people vulnerable to cybercrime - many devices today are connected to the web, including smart TVs, which can record everything said in a room.
"We need to ensure we understand the risk of these connected devices," said ISACA president Robert Stroud.
Hilary Chung, a Form Five student at Diocesan Girls' School, says she thinks students should keep the photos they upload onto social media private, so only their friends can see them. "You never know what people can do. Some may manipulate your photos, some may use your personal details," she says.
But mutual friends can still see the pictures if she tags her friends.
"We may share some hundred mutual friends, but I don't actually know them. That's just how Facebook works for us," she says.