Backdoor. AndroidOS. a, it is the most sophisticated piece of Android malware ever seen. It exploits multiple vulnerabilities, blocks uninstall attempts, attempts to gain root access, and can execute a host of remote commands. It uses a previously unknown vulnerability in Android that allowed it to take control of and maintain a foothold on infected Android devices. It can gain administrator privileges, making it virtually impossible for a user to delete it off a device. It is modular, with the ability to receive software updates directly from C&C servers controlled by the attackers.
Source: https://thehackernews.com/2013/06/most-sophisticated-android-malware-ever.html