When you need to charge your phone and see a USB port or an outlet, it’s tempting to use that outlet. But according to security firm Authentic8, you might want to think twice before you charge.

This is due to a kind of hacking called “juice jacking,” when someone hacks a port and accesses all the information like email, text messages, photos and contacts on phones connected to the port. A similar hack is called “video jacking,” when someone uses a hacked port to record everything you type and look at on your phone.

You may not know that the cord you use to charge your phone also sends data between your phone and other devices. When you plug your phone into an unknown port, there’s no way to know for sure that the port you’re using is safe. This includes public charging stations, but also places like the wi-fi access points you find in airports, planes and other public places.

At this week’s RSA security conference in San Francisco, Authentic8 conducted an experiment to see how many people would use public charging stations and found that 80% of attendees connected their phones without asking about security.