Android 4.2 contains a new security feature that allows Google to verify apps that users attempt to install from third-party sources. When installation is attempted a dialogue box will pop up that asks if you want to verify the app before installing. The option is turned on by default, but you can disable it in from the settings menu.
Google’s app verification is designed to keep apps from stealing your data and causing harm to your device. Google will take it upon itself to block installation of an app it deems to be particularly dangerous to Android’s security systems.
If you choose to have Google verify an app, you’ll also be sending Google your device ID, IP address, cookies, device information and the URL(s) of the app you choose to verify. Some may consider that a reasonable price in exchange for protection.