Czech Republic digital security company Avast has reported 47 games in Google Play for using hidden ads.

Currently, Google is investigating the reports and has removed 30 of the apps, which means 17 can still be installed. As part of the hidden ads adware campaign, the apps are disguised as games but will take users outside of the app to show different advertisements.

Overall, the reported apps have been downloaded over 15 million times. The most popular at one million installs each are Draw Color by Number, Skate Board - New, Find Hidden Differences, Shoot Master, Stacking Guys and Disc Go!.

What a discovery

The Prague-based company was able to detect the emerging problem through automatic detection software by Apklab.io, which was created due to a previous HiddenAds campaign found in the Android store.

"Campaigns like hidden ads may slip into the Play Store through obfuscating their true purpose or slowly introducing malicious features once already downloaded by users. It's difficult to prevent adware campaigns since actors use one-off developer accounts for each app," said Avast threat analyst Jakub Va.

"While Google has been a great partner to remove malicious apps, users need to remain vigilant as they download new apps on their devices and check for telltale signs of a bad app such as negative reviews, extensive device permission requests and more."