Once again, researchers have uncovered a major adware scheme on the Google Play Store. According to Trend Micro, threat actors managed to upload 85 malicious apps to the official Android app store. The apps gathered over 8 million total installs before they were removed.

Ecular Xu of Trend Micro said that “apart from displaying advertisements that are difficult to close,” the apps used “unique techniques to evade detection through user behavior and time-based triggers.” For instance, the apps would delete their icon from the home screen after installation and replace it with a shortcut that could not be used to uninstall the application. Despite receiving a lot of negative reviews, some of the apps had been installed over a million times.

Read more: 8 million Android users tricked into downloading 85 adware apps from Google Play