The next time you hop on an airplane, go to a concert, or just go out in a public crowd you may want to change a setting on an iPhone, iPad, or Mac computer. Apple’s Airdrop feature is causing problems, particularly on airlines, as numerous passengers report receiving unwanted and disturbing photos from strangers.

The iPhone’s Airdrop feature makes it easy to share photos with friends. Like if you’re all at an event, someone can Airdrop a group photo to everyone all at once rather than texting or emailing it to everybody one at a time. But pranksters and perverts are using Airdrop to send disturbing photos to people they don’t know.

In recent months, children and teenagers have Airdropped photos of crashed planes, weapons, and threatening messages to people on their flights. Multiple times men Airdropped pornographic photos of themselves to other passengers. how does this happen? How can some stranger send images to unsuspecting passengers?

For the uninitiated, If you have Airdrop turned on on an iPhone, iPad, or Mac computer, anyone near you can send an image using Bluetooth. And many people have Airdrop turned on to receive images from everyone without realizing it. On a recent flight, I could have sent a photo of my cat in my camera roll to nearly a dozen fellow passengers. I didn’t send it, but I could have and every one of those phones would have received it.

The image wouldn’t open automatically, those passengers would have gotten a notification that my phone was attempting to send an image and by tapping “accept”, the photo would display on their device.

To prevent it from happening to you, go to settings> general> “airdrop” to change the options. You can turn receiving off completely, keep it turned on for your contacts, or, turned on to receive images from everyone.

I’d recommend turning it on to receive images only from contacts or turn it off completely. You can always turn it on again if you know someone is trying to airdrop that photo of a family gathering.

And if you’re thinking of playing this prank, as some on airplanes have learned, it isn’t funny at all. It’s fairly easy to learn which phone is sending the image and depending on what you send, you can be arrested.