It goes without saying that the majority of smartphones and tablets out there are packed with free apps. Not only are the majority of the most “essential” mobile apps free by design anyway (social media, weather, etc.), but many of us also stock up on free games, apps for our favorite restaurants and stores, and other applications with the attractive price tag of $0. But are these apps actually free? Or do they carry a hidden cost?

No, that is not a reference to in-game purchases, though those are irritating. Instead, it’s a reference to a point made by a Kim Komando in a recent Fox News article. As Komando writes, “free apps often have a privacy cost” that remains hidden to most users. App developers are willing to give their programs away for free, but only because they can get their hands on user information with every download.

The information collected by these apps does, of course, depend on the program. Some track your online activities; others mine your contact list; many want to access your location, while some even take a look at your text messages. And while all of this sounds illegal, it probably is not. Ever skipped reading through the Terms & Conditions of a new app download and just tapped “Agree” to get to the app faster? If so, you have probably agreed to one or more of the invasive maneuvers listed above.

In her article, Komando references a recent Carnegie Mellon study, which compiled a list of 10 mobile apps that “request the most access to your smartphone or tablet’s hardware.” Some of the apps on that list are not surprising: Google Maps, for instance, needs to have access to your location information whenever you are using it, while Brightest Flashlight obviously needs to use the flashbulb on your device.

However, the list also includes seemingly random apps like Backgrounds HD Wallpaper, Dictionary.com, Mouse Trap, and Talking Tom Virtual Pet. It is not clear why any of these applications would need access to any of your hardware or information, and yet they request it anyway.

So how can mobile users retain their privacy while still taking advantage of free apps? One option is to read the Terms & Conditions.  Another is to take advantage of the case-by-case permissions feature that comes with iOS. The feature allows you to decide which pieces of information or hardware your apps will or will not be allowed to access. As Komando notes, though, there is no similar feature available for Android.