By KYW social media editor Melony Roy

PHILADELPHIA (CBS) – Do you know all of your teens Facebook friends? Chances are, neither does your teen. But there’s now an app to check if those friends are sex offenders.

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Pew Research reports the average teen has about 300 Facebook friends, but likely doesn’t know all of them well.

Rob Zidar, co-founder of “Third Parent” — a Flemington-based company that will audit your teen’s online activities, says the app “Friend Verifier” can be useful to teach teens and tweens the dangers of friend collecting:

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“When you log in you authorize the friend finder app to access your Facebook contacts and it check their names against the national database of sex offenders.”

Zidar says “likes,” “favorites,” and “retweets” are digital currency among teens:

“Not to pick on girls, but if you’re a teenage girl and you post a picture of yourself and you get two ‘likes,’ for a lot of teens out there, they’d delete that picture, so the bigger the crowd the better for that use of social media.”

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So even if your teens Facebook account is private, keep an eye on their friends list. Popularity is a common goal for teens and a network of 300 is not private.