Skype Hacking – Reverse Engineering Android Apps

By | November 11, 2013

It has been a long time since I did my last post. Time is short and intense and I have been living at a fast-pace =)

During one of my personal projects I decided to study the internals of Android and the potential of altering the Dalvik VM (e.g. Xposed framework and Cydia) and application behaviour.  Not going into detail about runtime hooking of constructors and classes like these two tools provide, I also explored the possibility of reverse engineering and modifying existing applications.

In the web you can find multiple tutorials on Android reverse engineering of applications but not many that do it with real applications that are often subject to obfuscation or with complex execution flows. So in order to learn I decided to pick a common application such as Skype and do the following:

  • decompile it
  • study contents and completely remove some functionality (e.g. ads)
  • change some resources (not described in presentation bellow)
  • recompile, sign and install.

Used tools include :

  • apktool – for (de)compiling android applications
  • jarsigner – for signing android applications
  • xposed – for intercepting runtime execution flow (will make public in future)

The following presentation describes the steps taken in order to completely remove the ads from skype. This includes any computation or data plan usage the ads consume. Please note the disclaimer of the presentation as this information is for educational purposes only.

Download (PDF, 1014KB)

Happy hacking! =)

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