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PITTSBURGH (KDKA) – More than a billion people around the world use Instagram and it’s especially popular with teens.

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Ask any teenager and they’ll tell you, Instagram is one of the most popular social media sites they use.

However, some of the accounts that have been trending lately could be jeopardizing their safety.

“Something about it is kinda creepy,” Indira Ortiz said.

She’s talking about the Instagram account called “I Know Exactly Who You Are” and there are many other accounts just like it.

(Photo Credit: CBS)

Here’s how it works:

An anonymous user entices teens to follow their account.

The user then messages the teen, telling them personal details about themselves such as where they go to school, what grade they’re in and who their friends are as a way to lure them in.

“I wanted to know that it was an actual true thing. Like, wow this guy actually knows, like is he a stalker or an actual person who knows everything or can hack something,” Ortiz said.

“I started following it and seeing if it was true and I messaged them asking them. I wanted to know if you knew who liked me,” Kimberly Rosil said.

Several teens say they follow the accounts for the thrill of a stranger revealing what they know about them.

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But, the danger comes when that stranger shares everything they’ve learned with thousands of other people on Instagram.

Cybersecurity expert Clifford Neuman said the people behind these accounts are likely snooping around the social media pages of the teens and their friends to get the info.

He said that’s why it’s important to understand the implications of what you post online.

“This information is now being disseminated in a less controlled manner and the same kind of information that is being used to entice kids in order to friend these pages could also be used by pedophiles or otherwise,” Neuman said.

Neuman says often, once the account holders gain a large number of followers, they repurpose their pages and sell them off.

So, who’s behind the creepy mask?

YouTuber Shane Dawson tried to get to the bottom of it in a Skype call.

Dawson: “Things that are impossible that you know, how do you find these things?”

Instagram Guy: “I basically just look at your picture and my brain tells me who you are, what you have done right and wrong in your life, and I just give that information back to you.”

Dawson: “So, like a psychic?”

Instagram Guy: “Yeah, basically.”

Not many people would buy that, but the curiosity is why these Instagram pages are becoming more and more popular.

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“Some people in the world want to hurt others, but I feel like this page is just for fun,” Ortiz said.