Products used for managing network traffic and restricting access to Web content represent a dual-use technology. While they were designed to improve performance and protect users from inappropriate content, these products are also used to censor the Web by authoritarian regimes around the globe. This dual use has not gone unnoticed, with Western governments placing restrictions on their export.Our contribution is to present methods for identifying installations of URL filtering products and confirming their use for censorship. We first present a methodology for identifying externally visible installations of URL filtering products in ISPs around the globe. Further, we leverage the fact that many of these products accept user-submitted sites for blocking to confirm that a specific URL filtering product is being used for censorship. Using this method, we are able to confirm the use of McAfee SmartFilter in Saudi Arabia and the United Arab Emirates (UAE) and Netsweeper in Qatar, the UAE, and Yemen. Our results show that these products are being used to block a range of content, including oppositional political speech, religious discussion and gay and lesbian material, speech generally protected by international human rights norms.
Content filtering technologies are often used for Internet censorship, but even as these technologies have become cheaper and easier to deploy, the censorship measurement community lacks a systematic approach to monitor their proliferation. Past research has focused on a handful of specific filtering technologies, each of which required cumbersome manual detective work to identify. Researchers and policymakers require a more comprehensive picture of the state and evolution of censorship based on content filtering in order to establish effective policies that protect Internet freedom. In this work, we present FilterMap, a novel framework that can scalably monitor content filtering technologies based on their blockpages. FilterMap first compiles in-network and new remote censorship measurement techniques to gather blockpages from filter deployments. We then show how the observed blockpages can be clustered, generating signatures for longitudinal tracking. FilterMap outputs a map of regions of address space in which the same blockpages appear (corresponding to filter deployments), and each unique blockpage is manually verified to avoid false positives. By collecting and analyzing more than 379 million measurements from 45,000 vantage points against more than 18,000 sensitive test domains, we are able to identify filter deployments associated with 90 vendors and actors and observe filtering in 103 countries. We detect the use of commercial filtering technologies for censorship in 36 out of 48 countries labeled as 'Not Free' or 'Partly Free' by the Freedom House "Freedom on the Net" report [26]. The unrestricted transfer of content filtering technologies have led to high availability, low cost, and highly effective filtering techniques becoming easier to deploy and harder to circumvent. Identifying these filtering deployments highlights policy and corporate social responsibility issues, and adds accountability to filter manufacturers. Our continued publication of FilterMap data will help the international community track the scope, scale and evolution of content-based censorship.
In this study, we take another look at 5 years of web censorship data gathered by the OpenNet Initiative in 77 countries using user-based testing with locally relevant content. Prior to our work, this data had been analyzed with little automation, focusing on what content had been blocked, rather than how blocking was carried out. In this study, we use more rigorous automation to obtain a longitudinal, global view of the technical means used for web censorship. We also identify blocking that had been missed in prior analyses. Our results point to considerable variability in the technologies used for web censorship, across countries, time, and types of content, and even across ISPs in the same country. In addition to characterizing web censorship in countries that, thus far, have eluded technical analysis, we also discuss the implications of our observations on the design of future network measurement platforms and circumvention technologies.
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