A post by Terry Zink on MSDN blogs outlines how Android devices are being used to send spam. According to Terry, the spammers has control of a botnet that lives on Android devices and which is capable of logging to the user’s Yahoo Mail account and send spam.
Read the full blog post here – http://blogs.msdn.com/b/tzink/archive/2012/07/03/spam-from-an-android-botnet.aspx