DROIT: Dynamic alternation of dual-level tainting for malware analysis

Taint analysis for Android malware has received much attention in recent research. Existing taint techniques operate either at Java object level or at deeper instruction level. Object-level tracking is suitable for malware written in Java byte-code, but not for native ones. Instruction-level tracking captures the finest data flow. However, it leads to obscure semantic reconstruction and low performance. In this paper, we present DROIT, a taint tracker which dynamically alternates between object-level and instruction-level tracking on demands. DROIT tracks data flow at Java object level in general. When its Dalvik VM exits the byte-code execution, DROIT automatically switches to instructionlevel tracking, and vice versa. The trigger-based DROIT can alternate between the two levels in an efficient manner, and can provide dual-level whole image of the data flow, rather than fragments. Tracking at the dual levels also eases the semantic reconstruction significantly. The experiment with Android information-stealing trojans showed that DROIT can handle Java-based malware, those composed in native code, and those alternating between the two levels (e.g., DroidKungFu), respectively.