Eight Years of Rider Measurement in the Android Malware Ecosystem

Despite the growing threat posed by the Android malware, the research community is still lacking a comprehensive view of common behaviors and emerging trends in malware families active on the platform. Without such view, researchers incur the risk of developing systems that only detect outdated threats, missing the most recent ones. In this article, we conduct the largest measurement of Android malware behavior to date, analyzing over 1.2 million malware samples that belong to 1.28K families over a period of eight years (from 2010 to 2017). We aim at understanding how Android malware has evolved over time, focusing on repackaging malware. In this type of threat different innocuous apps are piggybacked with a malicious payload (rider), allowing inexpensive malware manufacturing. One of the main challenges posed when studying repackaged malware is slicing the app to split benign components apart from the malicious ones. To address this problem, we use differential analysis to isolate software components that are irrelevant to the campaign and study the behavior of malicious riders alone. Our analysis framework relies on collective repositories and recent advances on the systematization of intelligence extracted from multiple anti-virus vendors. We find that since its infancy in 2010, the Android malware ecosystem has changed significantly, both in the type of malicious activity performed by malware and in the level of obfuscation used to avoid detection. Finally, we discuss what our findings mean for Android malware detection research, highlighting areas that need further attention by the research community. In particular, we show that riders of malware families evolve over time. This evidences important experimental bias in research works levering on automated systems for family identification without considering variants.