Do You See What I See? Differential Treatment of Anonymous Users

The utility of anonymous communication is undermined a growing number of websites treating users of services in a degraded fashion. The second-class treatment anonymous users ranges from outright rejection to limiting access to a subset of the service’s functionality or imposing such as CAPTCHA-solving. To date, the observation of practices has relied upon anecdotal reports catalogued by anonymity users. We present a study to methodically and characterize, in the context of Tor, the treatment anonymous users as second-class Web citizens. focus on first-line blocking: at the transport layer, through or dropped connections; and at the application layer, explicit blocks served from website home pages. Our draws upon several data sources: comparisons of Internetwide scans from Tor exit nodes versus from control hosts; of the home pages of top-1, 000 Alexa websites through every exit; and analysis of nearly a year of historic HTTP crawls Tor network and control hosts. We develop a methodology distinguish censorship events from incidental failures such as caused by packet loss or network outages, and incorporate of the endemic churn in web-accessible services both time and geographic diversity. We find clear evidence Tor blocking on the Web, including 3. 67% of the top-1, 000 sites. Some blocks specifically target Tor, while others result fate-sharing when abuse-based automated blockers trigger to misbehaving Web sessions sharing the same exit node.