Adware serves pop-up adverts which make money for its developers whenever the adverts are clicked. While adware is often more of an annoyance than anything else, the intrusive adverts can cause issues for users as the ads constantly run in the background, repeatedly interrupting use and draining battery.

However, the two malicious apps - Sun Pro Beauty Camera and Funny Sweet Beauty Selfie Camera, examined by researchers at Wandera - also came with a number of additional permissions that suggest that the apps could be used for more intrusive behaviour if desired.

Both apps requested to record audio, allowing the app to use the microphone to listen in to anything said near the device at anytime, as well as a number of permissions that allow the app to be persistent on the device.

Sun Pro Beauty Camera was initially released in September 2017 and in its two years in the Play Store was downloaded over a million times. Funny Sweet Beauty Camera appeared in July this year and was downloaded over 500,000 times in just two months.

In both cases, the app is the only app published by the named developer, but both managed to get through vetting for Google's official app store.