Symantec’s analysis suggests the MDK Trojan is a new variant of Android.Backscript. The code of MDK is very similar to Android.Backscript and they use the same certificate to sign APKs. However, unlike the previous versions, this new variant uses an Advanced Encryption Standard (AES) algorithm to encrypt data, like servers and commands, in a file.  MDK: The Largest Mobile Botnet in China | Symantec Connect Community