Of the Alexa top 1 million websites censored in China, 84.5% are blocked by IP address, meaning that even if both DNS hijacking and SNI filtering are fully circumvented, the vast majority of blocked sites remain inaccessible. Only 66 currently censored sites can be unblocked by ESNI alone (combined with an encrypted DNS channel), while 101,049 ESNI-supported sites remain blocked by IP.

As of July 2019, approximately 10.93% of the Alexa top 1 million websites support ESNI (all via Cloudflare CDN, which enabled ESNI across all its platforms in September 2018), with 92.56% of Cloudflare-hosted sites using encrypted SNI over TLS 1.3. However, fewer than 0.01% of observed TLS ClientHello messages in the wild contained an ESNI extension, revealing a severe gap between server-side readiness and client-side adoption.

§4.2, §5.1 evaluation

The paper identifies 47 Cloudflare IP addresses that are already blocked by the GFW despite being shared by at least 85 websites, contradicting the prior assumption that censors avoid blocking shared CDN IPs due to collateral damage. This suggests censors will accept significant collateral damage to block CDN-hosted content when the set of co-hosted non-forbidden pages is deemed manageable.

§4.3 detection

Monitoring ESNI-related censorship across 14 geographic regions — including Mainland China, Iran, UAE, South Korea, and 10 others — found no blocking of ESNI traffic or interference with ESNIKey retrieval via DNS TXT records as of mid-2019, contradicting a widely circulated report claiming South Korea had already blocked ESNI. Additionally, the GFW's residual censorship window after a triggered RST was measured at 60 seconds (down from the previously reported 90 seconds).

§4.4, §6 evaluation

In China's Great Firewall, SNI filtering is almost never the sole blocking mechanism: only 70 of the 21,446 SNI-filtered sites are exclusively censored via SNI. The GFW uses SNI filtering as a 'third gatekeeper' — applied after DNS hijacking and IP blocking — and maintains separate blacklists for SNI filtering and DNS hijacking, evidenced by 2,764 sites under DNS injection but not SNI filtering.

§4.1 detection

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.

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DNS censorship of encrypted protocols is inconsistent in both China and Iran. In China, Yandex resolvers are censored only when the SNI extension is present; omitting SNI bypasses censorship for these resolvers. In Iran, DoH requires SNI omission for Quad9, Google, Adguard, CleanBrowsing, and NextDNS resolvers, but works with SNI for Yandex and Cisco resolvers. These inconsistencies suggest resolvers have been accidentally missed by censors, highlighting the value of automated tools that trial all resolver-mode combinations rather than hard-coding a single strategy. The support evaluation found 47 resolvers supporting DoH, 16 supporting DoH3, and only 8 supporting DoQ out of ~65 tested.

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DPYProxy-DNS tested 8 circumvention modes against DNS censorship from vantage points in Iran (AS201295, Mashhad) and China (AS4837, China Unicom). In Iran, DoQ was entirely uncensored even with the SNI extension present; DoH3 worked for all Cloudflare and NextDNS resolvers. Iran's censor operates in-path (not on-path like the GFW), making the "Last Response" mode (wait 3s for the last UDP reply) ineffective in Iran but highly effective in China. Auto-mode averaged 12.32s (median 8.28s) in Iran and 13.78s (median 12.90s) in China to discover a working combination.

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DPYProxy-DNS's automated probe-and-select mode identified a working DNS circumvention in an average of 13.78 seconds (median 12.90s) in China and 12.32 seconds (median 8.28s) in Iran across 100 runs each; best-case startup was 0.32s (China) and 0.47s (Iran) when the first-tried combination succeeded, while worst-case exceeded 30.72s in China and 58.16s in Iran due to the slow Last Response mode (3s fixed wait per attempt) being selected early in the randomized probe order.

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Pakistan's PECA (Prevention of Electronic Crimes Act) and PTA (Pakistan Telecommunication Authority) regulations grant authority to block content without court orders, enabling the deployment of a persistent national filtering infrastructure. The report documents 11,000+ URLs blocked by PTA and confirms that VPN use and circumvention tools are among the targeted categories, with blocking orders issued under national security grounds.

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GFWeb tested 1.02 billion domains against the GFW over 20 months and discovered 943,000 pay-level domains blocked by HTTP filters and 55,000 by HTTPS filters — the largest GFW blocklist dataset ever published. The HTTP-to-HTTPS ratio (17:1) confirms that the GFW's HTTPS keyword-based and SNI-based blocking covers far fewer domains than its HTTP host-header blocking, likely because HTTPS blocks carry higher collateral-damage risk.

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