Android users trying to install mods for the wildly popular game title Minecraft may be unintentionally installing adware and malware to their devices.

According to new research from cybersecurity and anti-virus company Kaspersky Lab, over twenty apps available to download on Google’s Play store claiming to add additional content to the game were “malvertising,” which launches unwanted popup ads on a user’s device. The apps also take steps to conceal themselves on their target devices, making it difficult to identify, locate, and uninstall the malicious download.

The creators of the malware also posted dozens of fake reviews for each iteration of the apps, making them seem less suspicious.

Of particular concern is the popularity of the Minecraft franchise with children and young adults, who are often less cautious about the apps they choose to install. 

Google has since pulled fifteen of the twenty apps identified by Kaspersky. Of the five remaining on its official app store, at least one has been downloaded and installed over a million times.