Security is something very important these days. And Google is taking the extra step to give the massive amount of Android users it has safe. Android already has the ‘Verify apps’ feature. What this does is scans applications from outside sources and not from Google Play. But now, Google will make the ‘Verify apps’ feature continually scan your device for applications that are rather suspicious.
Chances are you will not ever be affected by a suspicious application, though. Google says “that fewer than 0.18% of installs in the last year occurred after someone received a warning that the app was potentially harmful.” So if you are downloading applications from somewhere other than the Play Store, just proceed with caution.
Source: Android Official Blog