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Encore: Lightweight measurement of web censorship with cross-origin requests

Author(s): Burnett, S; Feamster, Nick

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Abstract: Despite the pervasiveness of Internet censorship, we have scant data on its extent, mechanisms, and evolution. Measuring censorship is challenging: it requires continual measurement of reachability to many target sites from diverse vantage points. Amassing suitable vantage points for longitudinal measurement is difficult; existing systems have achieved only small, short-lived deployments. We observe, however, that most Internet users access content via Web browsers, and the very nature of Web site design allows browsers to make requests to domains with different origins than the main Web page. We present Encore, a system that harnesses crossorigin requests to measure Web filtering from a diverse set of vantage points without requiring users to install custom software, enabling longitudinal measurements from many vantage points. We explain how Encore induces Web clients to perform cross-origin requests that measure Web filtering, design a distributed platform for scheduling and collecting these measurements, show the feasibility of a global-scale deployment with a pilot study and an analysis of potentially censoredWeb content, identify several cases of filtering in six months of measurements, and discuss ethical concerns that would arise with widespread deployment.
Publication Date: 17-Aug-2015
Electronic Publication Date: 2015
Citation: Burnett, S, Feamster, N. (2015). Encore: Lightweight measurement of web censorship with cross-origin requests. 653 - 667. doi:10.1145/2785956.2787485
DOI: doi:10.1145/2785956.2787485
Pages: 653 - 667
Type of Material: Conference Article
Journal/Proceeding Title: SIGCOMM 2015 - Proceedings of the 2015 ACM Conference on Special Interest Group on Data Communication17 August 2015
Version: Author's manuscript

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