"Join this group and invite all your friends," is a message that children and young people are increasingly seeing on WhatsApp when joining new groups.
These can be hubs for illegal content and can be dangerous, says Kira Liebmann, a family coach in Germany advising parents on how they can protect children from threats online.
What are these sprawling WhatsApp groups about, how do they work?
Kira Liebmann: In WhatsApp groups, many people can exchange text messages, pictures and videos at the same time. These groups can include up to 1,024 members. They are very popular among schoolchildren who often create them without their parents knowing.
Kids can just add other children - often classmates - to these groups, sending "invitations." Whether these come from their classmates or from distant acquaintances. Often these come with the request, "Join this group and invite all your friends. We want to get a thousand members." Once in, they also add all their contacts without thinking twice, and the groups grow and grow.
Are these massive groups a problem for children and young people?
Liebmann: These groups are often quite chaotic, with children receiving thousands of messages within the space of a few minutes. People send around porn and images of war, they spread hate and bully each other, all of which you would want to protect your child from. They can also contain illegal content such as child pornography, and possessing it is a criminal offence.
No one moderates these groups so there is no one who can delete any chats with problematic content. The groups are so large that often it is also impossible to trace who started them. All that adds up to a situation where thousands of children and young people are overwhelmed with an unstoppable deluge of dubious content and are often unable to react appropriately.
Furthermore, the children's telephone numbers are visible to all of the members in these groups. Even if the child leaves immediately, their phone number is still visible, so strangers can contact them. That leads to young girls in particular constantly being contacted by people who claim to be 12-year-olds, asking them for photos, to share their address or even to meet up.
How can parents protect their children from all these dangers?
Liebmann: First of all, they should change the data protection settings on their mobile phones so that they cannot be added to groups without being asked. You also want to make children aware of the dangers of these groups - which could potentially contain not only their school friends but also criminals.
Parents should regularly monitor their children's online activities - at least until they are 14 years old. Build up a strong relationship of trust so children can turn to you immediately if something happens that worries them or seems suspicious. As a parent, you should look out for warning signs, whether your child is changing? Do they seem frightened or intimidated?
If you are concerned about a particular incident, do not hesitate to call the police, especially if you see illegal content. Cybergrooming, or initiating sexual contact with children and young people online, is a criminal offence.
If in doubt, it is better to err on the side of caution and go to the police once too often in order to protect your children.
