Downloaded by millions, three apps have been found by Avast researcher Filip Chytry that are designed to activate days after the apps were installed. The rogue applications—a game called Durak, an IQ test and a history app—had been downloaded millions of times.



Durak seems like a legit gaming app. However, Avast Software researchers said: “This impression remains until you reboot your device and wait for a couple of days. After a week, you might start to feel there is something wrong with your device.”

Specifically, every time users unlock their phones, the app displays persistent ads claiming the device and its data are at risk.

The delay makes it difficult for users to know what is causing the issue.

Chytry said: “I believe that most people will trust that there is a problem that can be solved with one of the apps’ advertised ‘solutions’ and will follow the recommended steps, which may lead to an investment into unwanted apps from untrusted sources."

“These security apps are, of course, harmless, but would security providers really want to promote their apps via adware?” Chytry said. “Even if you install the security apps, the undesirable ads popping up on your phone don’t stop.”

Google has removed the three offending applications identified by Avast from Google Play.