DexHunter: Toward Extracting Hidden Code from Packed Android Applications

The rapid growth of mobile application (or simply app) economy provides lucrative and profitable targets for hackers. Among OWASP’s top ten mobile risks for 2014, the lack of binary protections makes it easy to reverse, modify, and repackage Android apps. Recently, a number of packing services have been proposed to protect Android apps by hiding the original executable file (i.e., dex file). However, little is known about their effectiveness and efficiency. In this paper, we perform the first systematic investigation on such services by answering two questions: (1) what are the major techniques used by these services and their effects on apps? (2) can the original dex file in a packed app be recovered? If yes, how? We not only reveal their techniques and evaluate their effects, but also propose and develop a novel system, named DexHunter, to extract dex files protected by these services. It is worth noting that DexHunter supports both the Dalvik virtual machine (DVM) and the new Android Runtime (ART). The experimental results show that DexHunter can extract dex files from packed apps effectively and efficiently.