2023-raman-advancing
findings extracted from this paper
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Censored Planet measurements of psiphon.ca in AS6697 (Belarus) around the August 2020 Internet shutdown showed that Psiphon was initially blocked via connection timeouts during the shutdown itself, and then—several weeks after the shutdown ended—the censorship mechanism shifted to TCP RST injection. Outcome-typed measurement data made this two-phase mechanism change immediately visible without re-collecting any raw data.
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During the Belarus Internet shutdown of August 9, 2020, Censored Planet Echo measurements showed an increase of two orders of magnitude in test measurements failing at the TCP connection stage on the first day of the shutdown, alongside an order of magnitude increase in failed control measurements on the same day. Without comparing test measurements against control measurements that are expected to succeed regardless of content, these failures are indistinguishable from targeted website-level censorship.
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In Censored Planet DNS measurements of 75 .gov and .mil domains on April 11, 2021, only 36.06% of measurements from China resolved correctly. Of the failures, 19.06% returned SERVFAIL codes caused by US-based nameservers geoblocking Chinese recursive resolvers—server-side access control, not GFW censorship—causing prior studies that did not account for geoblocking to systematically over-estimate DNS blocking in China.
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The Censored Planet data analysis pipeline matched more than 60.89% of all HTTP-response data across four years of measurements to either a known blockpage fingerprint or a confirmed non-censorship fingerprint. Over 60 million individual measurements were specifically classified as expected Akamai CDN behavior—responses that previous work had routinely misclassified as censorship because Akamai's edge configuration returns connection timeouts or HTTP 301 redirects when the test domain and vantage-point server are both Akamai-hosted.
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Previous work reported that Myanmar ISPs selectively applied DNS blocking versus TCP/IP blocking, but analysis of the underlying data revealed they applied both concurrently. The apparent difference arose because some OONI volunteers bypassed DNS tampering by using public DNS resolvers (Cloudflare, Google Public DNS) and subsequently experienced IP-level blocking instead, making measurements appear selective when they were not.