Packet-Level Open-World App Fingerprinting on Wireless Traffic

Mobile apps have profoundly reshaped modern lifestyles in different aspects. Several concerns are naturally raised about the privacy risk of mobile apps. Despite the prevalence of encrypted communication, app fingerprinting (AF) attacks still pose a serious threat to users' online privacy. However, existing AF attacks are usually hampered by four challenging issues, namely i) hidden destination, ii) invisible boundary, iii) app multiplexing, and iv) open-world recognition, when they are applied to wireless traffic. None of existing AF attacks can address all these challenges. In this paper, we advance a novel AF attack, dubbed PACKETPRINT, to recognize user activities associated with the app of interest from encrypted wireless traffic and tackle the above challenges by proposing two novel models, i.e., sequential XGBoost and hierarchical bag-ofwords model. We conduct extensive experiments to evaluate the proposed attack in a series of challenging scenarios, including i) open-world setting, ii) packet loss and network congestion, iii) simultaneous use of different apps, and iv) cross-dataset recognition. The experimental results show that PACKETPRINT can accurately recognize user activities associated with the apps of interest. It achieves the average F1-score 0.884 for open-world app recognition and the average F1-score 0.959 for in-app user action recognition.