Although the Google Play store does a pretty good job of getting rid of apps that contain malware, it doesn’t do nearly as well when it comes to tossing out apps that contain adware. A new study from mobile security company Lookout shows that 6.5% of free Android apps on Google Play contain adware, which the company defines as software that will “display advertising outside of the normal app experience, harvest unusual personally identifiable information, or perform unexpected actions as a response to ad clicks” without a user’s consent. The firm also estimates that 1 million American Android users downloaded adware over the past year, so it seems that adware’s reach is fairly widespread.