Malicious apps that disable Android phones until owners pay a hefty ransom are growing increasingly malevolent and sophisticated as evidenced by a newly discovered sample that resets device PIN locks, an advance that requires a factory reset.

The app first tricks inexperienced users into granting it device administrator privileges. To achieve this, it overlays a bogus patch installation window on top of an activation notice. When targets click on the continue button, they really grant the malicious app elevated rights that allow it to make changes to the Android settings.