Android devices are very compatible with many apps, some web based and others installed on them, through which a lot of content from different online sources are consumed. By surfing the internet you put your device at risk of getting attacked by harmful viruses, spyware, Trojans and other harmful programs.

http://www.emoretech.com/top-10-best-antivirus-for-android-phone-download-2013-free/
The above are best antivirus for android phones but each passing day more there are being developed and this creates an even bigger pool to choose from.