Avast has discovered malicious apps in the Google Play store, some of which have been downloaded 5m-10m times.
Durak (gaming), IQ test and history app – all which have since been removed – were found to be dodgy, despite appearing ok and working fine for anything up to a month.
Andrei Mankevich, an independent game developer, originally alerted Avast to these three apps, and "dozens" more.
As Filip Chytry comments, following a quiet period where all appears well, the app then shows its true colours but, having laid dormant for a while, it’s difficult for users to work out where the problem lies.
“Each time you unlock your device an ad is presented to you, warning you about a problem, e.g. that your device is infected, out of date or full of porn,” he says.
The subsequent request for action to be taken brings customers, after approval, to harmful threats on fake pages such as dodgy app stores.
“An even bigger surprise was that users were sometimes directed to security apps on Google Play,” he says.
“These security apps are, of course, harmless, but would security providers really want to promote their apps via adware?”
Google seems to be removing these discovered apps from the Google Play store, but it does serve as a warning to users, beware of what you download.