This document discusses decompiling and reverse engineering mobile applications. It begins by explaining why mobile security is important due to growth in mobile usage and banking. It then covers different types of mobile applications and architectures that can be decompiled. The goals of decompiling are outlined as understanding application workings, finding sensitive data, bypassing checks, and analyzing algorithms. The methodology involves accessing executables, understanding technologies, deriving object code, class files, and function definitions. Demos are provided for Windows Phone, Android, Blackberry, and iOS applications. Obfuscation is discussed as a mitigation technique.