CenDTect, an unsupervised decision-tree system using iterative parallel DBSCAN, analyzed more than 70 billion Censored Planet data points (January 2019 – December 2022) and discovered 15,360 HTTP(S) censorship event clusters across 192 countries and 1,166 DNS event clusters across 77 countries. Manual validation against 38 known censorship events from news reports confirmed all human-identified events were recoverable from CenDTect's output. The system additionally identified more than 100 ASes in 32 countries with persistent ISP-level blocking and 11 temporary blocking events in 2022 correlated with elections, protests, and armed conflict.

CenDTect uses cross-classification accuracy — how well a decision tree trained on one domain's blocking pattern predicts another domain's blocking — as a distance metric to cluster domains that share the same blocking policy. This metric outperforms prior time-series approaches because it is interpretable (the resulting decision tree directly reveals the blocking mechanism: which ISP, which port, which protocol) rather than producing opaque anomaly scores. The approach scales to planetary-measurement volumes without requiring labelled training data.

§3 (CenDTect Design), §5.3 evaluation

Of 6,915,266 domains extracted from the 572 GiB Geedge Networks Leak (GNL), 298,955 censored domains (93.7% of all GNL-censored domains) appear in neither Tranco top-1M nor CitizenLab test lists. Measurements across China (Guangzhou/Nanjing), Myanmar, Pakistan, and Algeria confirmed censorship via DNS injection and SNI-based TLS connection termination. The GNL covers 25–62% of Tranco-censored domains across countries, showing substantial but incomplete overlap. This vendor-side ground truth reveals a censorship surface roughly two orders of magnitude larger than curated academic test lists.

2026-sheffey-geedge §4.1, Table 2 dpisni-blockingdns-poisoningmeasurement-platform

The paper introduces TMC, a remote measurement tool that infers domain-blocking status across DNS, HTTP, and HTTPS without requiring in-country vantage points, using only 38% Internet penetration in a country of 6 million people. TMC enabled the largest Turkmenistan censorship measurement to date by exploiting middlebox reflection properties observable from outside the country.

2023-nourin-measuring §TMC measurement-platformdpidns-poisoning

Analyzing over 3 million OONI network measurements (2016–2020) from 17 ASes covering 98.45% of broadband and 90.94% of mobile subscribers in Spain, the study detected 16 unique blockpages, 2 DPI vendors (Fortinet/Fortigate in Telefonica; Allot in Vodafone), and 78 blocked websites across copyright, political, civil-rights, and referendum categories.

2021-ververis-understanding §3, §4 dpidns-poisoningpacket-injectionsni-blockingmeasurement-platform

OONI's experiment-control methodology explicitly favors false positives over false negatives: it is preferable to generate more censorship candidate events for further investigation than to miss genuine interference. Mismatch between experiment and control data is not always a definitive signal of manipulation but is treated as sufficient cause for flagging, and data collection and analysis are treated as distinct phases.

2012-filast-ooni §4 Methodology measurement-platformdpikeyword-filteringdns-poisoningrst-injection

The June 2025 Iran shutdown—carried out during the Iran-Israel war beginning ~June 19—did not use BGP route withdrawals as in 2019. Instead, authorities applied service-level restrictions at the national border: DNS poisoning of foreign destinations, protocol whitelisting permitting only pre-approved domestic services, and DPI to block circumvention-tool traffic. Iran's international traffic fell roughly 90% while the country's BGP routes remained advertised, making the shutdown invisible to BGP-based monitoring systems. OONI measurement volume, which totalled 121,333 in June 2025, collapsed to under 200 submissions on June 19-20.

2025-iran-shutdown-measurement Executive Summary / §2 dpidns-poisoningport-blockingip-blocking

Article 19 documents that Iran's National Information Network (NIN / SHOMA) was designed with explicit reference to China's Great Firewall as a model, with institutional mirroring: Iran's Supreme Council of Cyberspace parallels China's Cyberspace Administration of China, and both governments share a "cyber sovereignty" doctrine used to justify domestic content controls and cross-border technology transfer. The report frames Iran's filtering infrastructure as deliberately architected to replicate GFW capabilities, not as an independently developed system.

2026-article19-tightening-the-net §2, §3 dpisni-blockingdns-poisoningip-blockingbgp-hijackthrottling