For those of you who don’t know what a Botnet is, it is a collection of compromised computers connected to the internet. In this case – the infected Android devices are the computers. The controller of these computers (bots) can use them to do his bidding i.e. send out spam email or launch denial-of-service attacks.
While the researcher doesn’t mention what apps are causing these Android devices to be compromised, he assumes that they’re probably cracked or hacked versions of legitimate apps that users have resorted to installing to avoid paying premium for a proper version of the app on the Google Play Store. So for those of you who refuse to pay for legitimate apps, be careful of what you install on your Android device in the future (while the Play Store isn’t 100% free of malware, the chances of picking one up are lower if you get your apps there as opposed to some warez site).