Whether they favor WhatsApp, Facebook Messenger, Kik or WeChat, your kids likely have ditched the world of traditional SMS to send text, video, photos and even audio chats to friends from their mobile devices. But do you — or your kids — know whom they’re really talking to online?

Related: 3 Apps to Monitor Your Kids’ Online Behavior

Messaging applications have no way of distinguishing between a person using his or her real first and last name and a person posing as someone else. So while your teen or tween may think she’s talking to the friend of a cute guy at school, the reality could be something very different.

In July 2015, a 14-year-old Virginia girl snuck out of her home, stole her father’s SUV and picked up a 41-year-old man who is a known sex offender, WTVR CBS 6 reported. “It looks like both the child and the suspect met on an online app called Kik," Surgoinsville Police Chief James Hammonds told the TV station. “These kids talking to these people on these chat apps and they really don’t know who they are talking to. It is really a dangerous thing.”

The Kik app has been on the receiving end of bad press for issues around child pornography. In January 2015, a Nebraska man was arrested and charged with distributing child pornography on Kik. In May 2015, a Massachusetts man was arrested and charged with the same crime. And in June 2015, a Virginia Beach man was sentenced to 10 years in prison for trading child porn on Kik.

In March, Kik said it will begin using Microsoft’s PhotoDNA Cloud Service to detect and report child exploitation images on its service.

Related: 7 Ways to Keep Your Kids Safe Online

The United States Computer Emergency Readiness Team (US-CERT) says that because messaging apps facilitate anonymity, it’s easy for people to misrepresent themselves — to both kids and adults.

“Adults often fall victim to these ploys,” US-CERT said in a statement in 2011, “and children, who are usually much more open and trusting, are even easier targets.”

Nearly all messaging apps require kids to be 13 years old to sign up, though they need parental permission. But spoofing permission is as simple as accessing an email account and clicking a link.

Talking to your kids to make sure they’re using caution and acting appropriately is your best defense, according to OnlineOnGuard.gov, a Homeland Security website. This means no sexting — they not only risk their reputation, but they may be breaking the law by sending explicit photos of someone under 18. It means ignoring texts from people they don’t know, and never posting their cellphone number online. Finally, kids should block any number that sends inappropriate messages, OnlineOnGuard.gov recommends.

Related: 5 Apps That Help You Keep Tabs on Your Kids

Don Reisinger is a longtime technology journalist and product reviewer.