Galaxy Z Flip 4 Preorder Quest 2: Still the Best Student Internet Discounts Best 55-Inch TV Galaxy Z Fold 4 Preorder Nintendo Switch OLED Review Foldable iPhone? 41% Off 43-Inch Amazon Fire TV
Want CNET to notify you of price drops and the latest stories?
No, thank you

Free Android apps could hijack your phone

Those annoying pop-up ads are back. This time, they're on your smartphone, and they're badder than ever. Here's how you can avoid aggressive adware on your mobile device.

Now playing: Watch this: Stamping out aggressive mobile app ads

Downloading free Android apps could make you vulnerable to aggressive adware, according to San Francisco-based security firm Lookout.

In fact, as much as five percent of those free apps have spammy ads that may be parceling out your information to third parties according to CTO Kevin Mahaffey.

That number may seem small at first, but not after you consider how many hundreds of millions of times those free apps are downloaded. To combat the problem, Lookout has developed its own app that scans other apps to tells you which ones are engaging in bad behavior. It's up to you to delete the offender(s).

The Android platform is the Wild West, and the good, the bad and the ugly are all present in abundance. The good, of course, is some seriously creative app development and an open platform that allows for some very cool innovation.

The bad, though, is less oversight when it comes to advertisers. The result can be apps that download themselves onto your device or send fake messages that appear to be texts and pop up on your screen even when the app isn't running.

And then there's the ugly, the possibility of malware that can steal information from your phone, like your current location or banking information, and send it to its creator. Lookout calls the practice "bad behavior" and has developed a set of rules for identifying apps that behave badly.

Compared to Android, Apple's App Store has more stringent rules limiting what free app developers can get away with and the types of allowable advertising. That might mean fewer new apps hitting the app store. But when it comes to protecting its users, Lookout says Apple isn't willing to compromise.