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If you think you know what naughty shenanigans your teenager is up to on the Interwebs, you'd better sit down because I have some bad news for you.

According to a June 2012 survey conducted by McAfee, more than 70 percent of teens hide their online behavior from their parents. (And some of those who say they don't were probably lying.) Meanwhile, less than one in five parents are aware that their teens are viewing porn, uploading racy photos, or chatting with total strangers.

In fact, the scariest things on the Internet are the messaging, photo sharing, and dating apps you've probably never heard of. Forget Facebook: Here are five of the most troubling Web and mobile apps your teens may be using.

Kik Messenger

This alternative texting service let your teens chat and swap pictures while bypassing your wireless provider's SMS service. So if you're checking your child's normal texting history for signs of misbehavior, you won't find any. Kik's terms of service ban pornography and nudity, but a search for “kik nudes” offers copious exceptions to these rules. Kik offers a guide for parents, but it's not terribly helpful. If you want to see what your child has been up to on Kik, you'll have to take their smartphone away and launch the app to see for yourself. Other popular alternatext apps include WhatsApp, TextNow, and Viber.

Snapchat

Five Mobile Apps That Should Scare the Pants Off Parents

Every day, some 400 million photos are shared via Snapchat; those photos then disappear, as Snapchat has them automatically self-destruct in ten seconds or less. In theory, it's a clever compromise between teenagers' voyeuristic narcissism and parents' desire to not have naked photos of their loved ones flying around the Intertubes. The problem? Apps that let others capture those supposedly temporary images and post them online are now widely available. Snapchat recently began offering a “Stories” feature that lets photos survive for up to 24 hours – offering even more opportunities to harvest images. Not surprisingly, Snapchat imitators (like Wire, Wickr, and Poke) are popping up everywhere.

Vine

For the most part, this app serves up endlessly looping six-second videos of cute pets and teens mugging for their smartphone cameras. But it also demonstrates just how much porn one can pack into six seconds. Following an uproar about naked naughty bits when it launched last January, Vine Labs removed the ability to search for adult hashtags like #XXX or #NSFW, but the videos are still there. Worse, anyone can search for teens, follow them, log their locations, leave comments, and try to connect with them via other services. Instagram, which officially bans nudity and sex-related hashtags, isn't much better.

ChatRoulette

This groundbreaking site lets anyone engage in video chat via webcam with random strangers. Users under 18 are prohibited, as is nudity, but nobody's checking IDs at the door or making sure everyone is wearing pants (trust me, they aren't). And if you do get booted for violating those terms, there are lookalike services (like Omegle, ChatRandom, or DirtyRoulette) with even fewer restrictions.

Tinder

Hookup apps like Tinder let you scroll through images of other members and flag the ones you like. If they also like you, you're both notified, and then you can contact each other and do what comes naturally. There are dozens of similar apps with names like Blendr, Grindr, Down, Skout, Swoon, and Pure. The problem? While some services require users to be 18 or older (Tinder's minimum age is 13), I've yet to find one that actually verifies anyone's age. Is your little angel hooking up with strangers? It doesn't get any scarier than that.

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What can you do to stop your kids from getting into trouble on these troublesome apps? You may need to activate parental controls on their devices to keep them from installing apps without your approval, or make sure all app purchases go through your account, not theirs.

If they do use these apps, make sure they don't do it unsupervised – no matter how much they kick and scream about it.

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