Many teens will use an app to text rather than using their phone company's texting plan -- so parents never find out.
"It's a lot harder to monitor texting on a app than it is on a phone because on a phone, at the very minimum, you can check your bill and see who your kids are texting with and on an app there's no way to call that up," said Colby Zintl, vice president of communications at Common Sense Media.
Commonsense Media is a non-profit organization that provides age-based media reviews. The company reviewed one of the most popular texting apps called Kik and found some safety concerns.
"There's group texting, you're inserting a profile and talking about yourself and then there some app plugins that make us a little uncomfortable," said Zintl.
There is a plug in on Kik called Oink Text that opens users up to strangers.
"You press the button to activate Oink Text and up roles a bunch of people within the Kik environment who you may or may not know and you can start a chat with them," said Zintl.
Another popular app with teenagers is called Snapchat. You take a picture and send it to a friend who has up to 10 seconds to view it before it disappears.
"When Snapchat was released the press called it the sexting app because it would allow kids to send these pictures and there would be no record of the photos that were sent," said Zintl.
But pictures don't necessarily disappear. In Snapchat's privacy statement the company warns users that it is not able to guarantee messages will be deleted in all instances. That's because users can capture a photo before it vanishes by taking a screen shot of it.
"I know that some people use it for sending funny photos and stuff, but I know some other people use it for sending sexual or inappropriate photos," said Harvey Hunerberg of Fairfax.
iFunny trends very high in the iTunes app store. Users can create their own comic strips or post photos and add captions. It can be used as a creative tool, but parents be warned.
"On the flip side it's an open source environment so kids are exposed to a lot of humor that they may or may not be ready for," said Zintl.
Most teens entertain themselves by flipping through what others have created on iFunny and forward what they like to friends. But parents should know that iFunny is rated for 17-years-old or higher.
"I usually save them to my pictures on my iPod and then sometimes I post them on Instagram," said Liam Jay of Fairfax.
"Things that one kid may see as funny could actually be a cyber-bullying incident where it's mocking someone's behavior, mocking someone's appearance," said Zintl.
iFunny says that they require users to follow certain guidelines when they submit photos and captions that include no sexually explicit content. The company made clear to us that they don't tolerate any content that violates the rules spelled out in their user agreement.
7 On Your Side contacted all the other companies named in this report and they all the other companies named in this piece and they all either declined to respond or never got back to us. Every app has a different privacy statement and you should expect everything you do on an app will be shared not only with friends but potentially with strangers. You should never assume your information is private.