On the surface, these stealth gaming apps appear to have other, more mundane functions, but of course once you actually install them, their true natures become readily apparent. Researchers found one app that was described as a hub for holiday information but once installed, its only function was to redirect users to a lottery system.
Unfortunately, it's a strategy that pays from the standpoint of the developers. Some of the apps discovered to be little more than shells were spotted in Top 100 lists. Many had been rated more than a hundred thousand times, which gives a sense of the scope and scale of the problem.
Google has taken note of the trend and has begun ruthlessly removing any apps that employ this kind of strategy, with Apple taking a similar stance. Unfortunately, about the best the two tech giants can do is clean up the mess after the fact, because many of the app developers making use of this redirect strategy have gotten quite cunning about it. They are deploying an app that appears perfectly normal and then flipping a virtual switch to activate its redirect features once it has been inspected by Google and Apple, respectively. That, of course, makes it virtually impossible to spot on the front end.
The best thing you can do to prevent downloading such an app is to carefully read and heed the user reviews. It's certainly not a perfect solution, but it's better than nothing.