Google’s security services for Android increased protection for users and improved visibility into attempts to exploit Android. Ongoing monitoring by Verify Apps found that efforts to deliver Potentially Harmful Applications (PHAs) continued at low levels throughout 2014, less than 1% of all devices had a PHA installed. Fewer than 0.15% of devices that download only from Google Play had a PHA installed. Expanded protection in Verify Apps and Safebrowsing also now provides insight into platform, network, and browser vulnerabilities affecting Android devices. Exploitation attempts were tracked for multiple vulnerabilities, and the data does not show any evidence of widespread exploitation of Android devices.
Google’s report on Android Security is available here - https://static.googleusercontent.com/media/source.android.com/en//devices/tech/security/reports/Google_Android_Security_2014_Report_Final.pdf