Google is rolling out a new update to Android that means its operating system will start continually checking its host device for harmful apps.The company says the update will enhance Android's Verify Apps service to make sure apps installed both inside and outside of Google Play are "behaving in a safe manner." Prior to the update, Verify Apps, which was introduced to Android in 2012 and Google says has been used more than 4 billion times, only scanned apps during their installation.

Android users who apply the update will see a warning on their device if they have a potentially dangerous app. These warnings may be seen more regularly by people who sideload software or download apps from unregulated marketplaces, but Google says most users will never spot any acknowledgement of the new layer of protection. Unsafe applications are rare, the company says, and the "risk is minuscule." Before the update, Android would only show such warnings when users first tried to install harmful software, an approach the company says was effective at stopping people from infecting their devices. According to Google, "fewer than 0.18 percent of installs in the last year occurred after someone received a warning that the app was potentially harmful."