SFMap: Inferring services over encrypted web flows using dynamical domain name graphs

Abstract

Most modern Internet services are carried over the web. A significant amount of web transactions is now encrypted and the transition to encryption hasmade it difficult for network operators to understand traffic mix.Thegoal of this study is to enable network operators to inferhostnames within HTTPS traffic because hostname information is useful to understand the breakdown of encrypted web traffic. The proposed approach correlates HTTPS flows and DNS queries/responses. Although this approach may appear trivial, recent deployment and implementation ofDNS ecosystems have made it a challenging research problem; i.e., canonical name tricks used by CDNs, the dynamic and diverse nature of DNS TTL settings, and incompletemeasurements due to the existence of various caching mechanisms. To tackle these challenges, we introduce domain name graph (DNG), which is a formal expression that characterizes the highly dynamic and diverse nature of DNS mechanisms. Furthermore, we have developed a framework called Service-Flow map (SFMap) that works on top of the DNG. SFMap statistically estimates the hostname of an HTTPS server, given a pair of client and server IP addresses.We evaluate the performance ofSFMapthrough extensive analysis using real packet traces collected from two locations with different scales.Wedemonstrate thatSFMapestablishes good estimation accuracies and outperforms a state-of-the-art approach.