These Android apps were clicking on ads behind your back

A notepad app and a fitness app downloaded on more than a million devices has been secretly clicking on ads without people knowing for nearly a year, security researchers found.

The apps, developed by a company called Idea Master, offered tools to help people lose weight and organize their lives, but were actually popping up ads off-screen and clicking on them multiple times per day, researchers from cybersecurity company Symantec said on Thursday.

The apps' developer didn't immediately respond to a request for comment. Idea Master has since been banned from the Play Store, Google's platform for Android apps, and both apps have been removed.

The apps were "Idea Note: OCR Text Scanner, GTD, Color Notes" and "Beauty Fitness: daily workout, best HIIT coach." More than 1.5 million people downloaded both apps, which were on Google's Play Store as recently as Aug. 23.

Android has an uphill battle keeping malware and adware off its Play Store -- especially compared with Apple's App Store for iO -- because of its open ecosystem. You might be able to do more on an Android device, but that freedom also extends to potential hackers. Android's security program has fixed issues with more than 1 million apps in the Play Store in the five years it's been active, but new attackers continue to pop up with different ways of hiding on people's devices.

The ad-fraud taking place on Idea Master's apps went unnoticed for so long because its code was hidden in Android packers typically used for protecting intellectual property, the researchers said.

Once installed, these apps display the ads outside of the device's display view, and are clicked on automatically, committing ad fraud and draining resources from a person's device. These ads take up battery life and mobile data usage on people's Android devices without a person even being aware of it.

Even before researchers discovered the ad fraud, people who downloaded the apps noticed and voiced their concerns in the apps' reviews. A review on the notes app from Aug. 5 said that the app was useful, but it had too many ads and that it was slowing down the device.

Another review on the notes app called the ads disruptive and irritating. And those were just the ads that the users saw.