403 Forbidden: A Global View of CDN Geoblocking Allison McDonald Matthew Bernhard Luke Valenta University of Michigan University of Michigan University of Pennsylvania∗
[email protected] [email protected] [email protected] Benjamin VanderSloot Will Scott Nick Sullivan University of Michigan University of Michigan Cloudflare
[email protected] [email protected] [email protected] J. Alex Halderman Roya Ensafi University of Michigan University of Michigan
[email protected] [email protected] ABSTRACT 1 INTRODUCTION We report the first wide-scale measurement study of server- Researchers have devoted significant effort to measuring side geographic restriction, or geoblocking, a phenomenon and circumventing nation-state Internet censorship (e.g., [23, in which server operators intentionally deny access to users 39, 49]). However, censorship is not the only reason why from particular countries or regions. Many sites practice online content may be unavailable in particular countries. geoblocking due to legal requirements or other business Service operators and publishers sometimes deny access reasons, but excessive blocking can needlessly deny valuable themselves, server-side, to clients from certain locations. content and services to entire national populations. This style of geographic restriction, termed geoblocking [45], To help researchers and policymakers understand this may be applied to comply with international regulations, phenomenon, we develop a semi-automated system to detect local legal requirements, or licensing restrictions, to enforce instances where whole websites were rendered inaccessible market segmentation, or to prevent abuse. due to geoblocking. By focusing on detecting geoblocking Geoblocking has drawn increasing scrutiny from policy- capabilities offered by large CDNs and cloud providers, we makers. A 2013 study by the Australian parliament concluded can reliably distinguish the practice from dynamic anti-abuse that geoblocking forces Australians to pay higher prices and mechanisms and network-based censorship.