The challenge encourages children to add a contact called “Momo.” When they do, they will come face-to-face with a creepy picture of a Japanese sculpture. Then, “Momo” starts to threaten the child, claiming to know personal information and making clear-cut threats.

“Like this ‘Momo’ thing could say, ‘Well if you don’t do X, then we’ll hurt your sister Sally,’ or something like that,” said Hatter.

In one case out of Argentina, police believe “Momo” intimidated and bullied a 12-year-old to the point she took her own life.

“I think it’s a legitimate thing to be concerned about,” said Hatter. “As a parent, I find it disturbing. I have a 10-year-old, and I will definitely be having a conversation with him about this.”

Tech experts said the best thing parents can do is educate themselves about it and educate their children by telling their kids what the challenge is and by ensuring they know the threats, if presented to them, are not real.

“You gotta know what your kids are doing,” said Hatter. “You gotta warn them about this kind of thing.”

Most of all, experts like Hatter suggest monitoring who your kids are talking to because you never know who could really be on the other side of the screen.

“It’s unfortunate that sick people take advantage of the technology and tools to do this kind of thing,” said Hatter.

Hatter said there is software available that can block certain smartphone apps should parents choose to do so.

A WhatsApp spokesperson released a statement on the matter, saying: “WhatsApp cares deeply about the safety of our users. It’s easy to block any phone number, and we encourage users to report problematic messages to us so we can take action.”