CacheLoc: Leveraging CDN Edge Servers for User Geolocation.

In nowadays' Internet, websites rely more and more on obtaining users' geolocation to provide customized services. However, besides Internet giants such as Google, who retains a large amount of detailed user information, most websites still rely on IP addresses for user geolocation, which is proven inaccurate and misleading by existing studies. In this paper, we propose a novel approach, namely CacheLoc, for coarse-grained user geolocation leveraging widely-deployed content delivery networks (CDNs). This work is motivated by the fact that CDN providers deploy a number of edge servers that are geographically distributed across the world. Many of these edge servers are assigned with unique identifiers that are tied to their location, which can be easily retrieved by inspecting HTTP responses headers served by these edge servers. As a result, a website can infer coarse-grained user location by asking a user to send an HTTP request to an arbitrary domain that is known being served by a CDN, and inspecting the corresponding responses. To evaluate the usability and accuracy of the cache-based user geolocation, we conducted practical experiments based on a commercial VPN with over 160 endpoints distributed in 94 countries. Our experiments demonstrate that cache-based geolocation can achieve at least accurate country-level granularity in the regions where CDN edge servers are densely deployed. Our work sheds light on a novel light-weight and self-contained user geolocation solution.