Security on Android
Android takes a multi-layered approach to security:

Prevent. Apps in Google Play are scanned continuously to block harmful apps and policy violators. You can also choose to have apps installed from other sources verified.
Control. App “sandboxes” keep apps from accessing other parts of your tablet’s operating system, or each other, unless you give permission at installation. Screen lock and encryption help prevent unauthorized access to the entire tablet.
Defend. Once identified, dangerous apps can be removed remotely.