Android botnet discovered by Microsoft engineer

What are the odds of an Android botnet being detected by a Microsoft engineer rather than Google or a security firm? We believe, the chances of such a scenario are pretty low. Having said that, we must admit that this has actually happened. Today, Microsoft anti-spam engineer Terry Zink discovered an Android botnet that uses the device to spread spam on an industrial scale. He posted more details of this discovery on his official MSDN blog. He noted that after analyzing multiple samples, he found one common thread, a digital signature which read “ Sent form Yahoo! Mail on Android.”
He was pretty confident that the effected users were using a spurious Android app that was riddled with malware.  ”I am betting that the users of those phones downloaded some malicious Android app in order to avoid paying for a legitimate version and they got more than they bargained for, either that or they acquired a rogue Yahoo Mail app.”