You may be one of the millions of users who downloaded adware-infected Android apps through the official Google Play Store.
Once installed, these malicious apps prevent their detection, serve full-screen ads on the device, and send back data in the background to potentially allow more malicious software on the device, TechCrunch reports.
In total, 42 apps containing adware have been downloaded over 8 million times since their release on July 2018. Some of these apps include Video Downloader Master, Ringtone Maker Pro, SaveInsta and Tank Classic. Google has since removed these apps.