WASHINGTON (WUSA) -- Downloading free Android applications could put your phone and security at risk. According to the security firm Lookout, about five percent of free Android apps can infect your phone. 

Spam ads to pop up on your screen even if the application is closed. Some bad apps can even access your personal information and sell it to third parties.

Keep in mind, Lookout has skin in this game because they have developed their own application that can scan other apps for bad behavior.