The automated probe list generation system discovered 45.79 potentially blocked domains per 1,000 domains crawled, compared to 4.11 for FilteredWeb — over 10× higher efficacy. It uncovered 1,490 potentially blocked domains in crawls of just 71,960 URLs, versus 1,255 blocked domains found by Hounsel et al. in crawls of 1,000,000 URLs, with 1,473 of the 1,490 domains not overlapping with prior work.

GFW verification tests confirmed over 90% of OONI-detected DNS anomalies as true blocks: 429/457 domains in Beijing and 422/461 in Shanghai. In total, 527 unique domains were confirmed censored via DNS, HTTP, and HTTPS filters; an additional 718 domains suspected blocked due to IP-address-level blocking of their hosting servers rather than domain-level entries.

§5.6 detection

Only 36.66% of the 139,957 source list URLs (51,313) survived sanitization as live, meaningful pages, with 18,911 URLs removed for lack of content and many more for dead links — underscoring how rapidly manually curated probe lists decay. In Beijing and Shanghai, over 20% of known domains were consistently inaccessible, versus fewer than 4.5% at all other vantage points, and over 68% of known domains remained blocked, suggesting censored topics stay sensitive even as URLs go stale.

§3.1, §5.2 evaluation

Among inaccessible URLs that also triggered OONI anomalies, approximately 58% were generated by the Top2Vec-Trends pipeline (combining Top2Vec topic modeling with Google Trends keyword expansion), while LDA-TFIDF and Top2Vec alone each accounted for only 13–14%. BERTopic-generated pages were least effective at producing censored candidates.

§5.4 evaluation

VPS-based vantage points in Singapore and India detected censorship patterns similar to 'free' locations, failing to observe blocking known to be enforced by local ISPs following government directives. This occurred because ISP-level censorship is implemented per-carrier rather than centrally, and the VPS provider's ISP did not enforce those blocks — confirmed by re-testing from a residential IP that did observe the expected blocks.

§6.2 detection

Naive interference measurement systematically misclassifies CDN geographic routing as blocking (and vice versa): when China or Russia resolves twitter.com to a non-US IP, a naive detector must decide whether that is a CDN point of presence or interference. Joint iterative analysis of DomainSimilarity and IPTrust scores is required to separate authentic CDN footprints from block-page redirections.

2016-scott-satellite §1, §2.4, §2.4.1 dns-poisoningip-blockingmeasurement-platform

Applying a regional binomial hypothesis test (p=0.7, significance 0.05) to Encore measurements independently confirmed censorship of youtube.com in Pakistan, Iran, and China, and of twitter.com and facebook.com in China and Iran, validating passive cross-origin measurement against prior independent reports of filtering.

2015-burnett-encore §7.2 measurement-platformip-blockingdns-poisoning

In 8,573 controlled testbed measurements across image, stylesheet, and script task types, Encore produced zero false negatives and a ~5% false positive rate in India (attributed to unreliable network connectivity rather than filtering), establishing that cross-origin browser probes reliably detect DNS, IP, and HTTP filtering under stable network conditions but require aggregation to control noise.

2015-burnett-encore §7.1 measurement-platformdns-poisoningip-blocking

Over a 14-day evaluation in April 2011, CensMon tested 4,950 unique URLs from 2,500 domains across 174 agents in 33 countries, detecting 951 unique URLs from 193 domains as filtered. Manual verification of all 193 flagged domains found only 3 false positives, demonstrating high precision for an automated distributed monitor.

2011-sfakianakis-censmon §4.2 measurement-platformip-blockingdns-poisoningkeyword-filtering

CensMon detected zero instances of partial web-page content filtering across 4,950 tested URLs during April 2011, indicating that censors at that time uniformly applied coarse-grained techniques — full URL block, IP blacklist, or DNS hijack — rather than inline content modification at the sub-page level.

2011-sfakianakis-censmon §4.2 keyword-filteringip-blockingdns-poisoningmeasurement-platform

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