According to the report from Cisco, the most widely encountered form of malware on Android is Andr/Qdplugin-A, which is usually introduced to an Android device while disguised as a legitimate app in unofficial app stores. So here is a tip, stick to the Google Play Store and that should reduce the odds of your phone getting infected.
Apple's iOS fared much better, obviously, and this is reflected in the fact that Cisco's report was brought to the attention of those who follow Phil Schiller's Twitter page. Schiller, as most of you know, is Apple's senior vice president of worldwide marketing.
Android devices are the most targeted with malware attacks
1. 71% of web-delivered malware is targeted at Android devices
2. The Andr/Qdplugin-A virus is the most encountered by Android devices
source: @pschiller via GigaOM