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.

All major browsers (Firefox, Chromium) issue an unencrypted DNS-over-UDP query to resolve their configured DoH resolver's domain before initiating any encrypted DNS session. In Iran, nearly all tested DoH resolver domains are directly censored at the DNS layer (returning block-page IPs), which renders browser-native encrypted DNS ineffective regardless of whether the underlying encrypted protocol would otherwise succeed. Additionally, browsers always include the SNI extension in TLS handshakes with DNS resolvers even though no tested resolver requires it.

§7 detection

The GFW operates as an on-path censor that injects forged DNS responses faster than the real resolver but cannot suppress the legitimate response from also arriving. Waiting approximately 3 seconds and accepting the last-received UDP response circumvented GFW DNS injection for 40 of 41 tested public resolvers in China; the single exception (Cloudflare 1.1.1.1) was IP-blocked via packet dropping rather than injection racing.

§6.2.1 defense

Iran's DNS censorship is largely ineffective against encrypted DNS: DoQ is not censored at all (with or without SNI present), DoH3 works for all tested Cloudflare and NextDNS resolvers, and most DoT/DoH resolvers work when the SNI extension is omitted. Iran's censorship of unencrypted DNS is in-path (queries never reach the real resolver), which means the GFW-style 'last response' technique fails entirely in Iran because the client's original query is dropped before reaching its destination.

§6.2.2 evaluation

TCP segmentation — splitting DNS-over-TCP messages into 20-byte fragments — successfully circumvented DNS censorship for 40 of 41 tested resolvers in China. In Iran, TCP segmentation is inconsistently effective: it succeeds in some scan runs and fails entirely in others, suggesting the Iranian censor can reassemble TCP fragments when processing capacity permits.

§6.2.1, §6.2.2 defense

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

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.

2026-lange-towards §6.2, Table 2 dns-poisoningsni-blockingip-blocking

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.

2026-lange-towards §6.2, §6.3 dns-poisoningsni-blockingip-blocking

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.

2025-amnesty-pakistan-shadows §2, §4 ip-blockingsni-blockingdns-poisoning

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.

2024-hoang-gfweb Abstract, §5.1 dpidns-poisoningip-blockingkeyword-filteringsni-blocking

Chinese-language Wikipedia views grew from 12.8 million per day in December 2019 to 13.9 million during the Wuhan lockdown (24 January–13 March) and peaked at 14.7 million per day from mid-February through April 2020; the crisis disproportionately increased views of pages selectively blocked by the Great Firewall prior to 2015, of historical Chinese leaders since Mao, and of current officials — categories expected only under a gateway effect — and these elevated levels persisted through May 2020.

2022-chang-covid-19 Crisis Provided a Gateway to Censored Political Information / Fig. 3 and Fig. 7 ip-blockingsni-blockingdns-poisoning