GoAgent, the most widely used circumvention tool among the 1,175 surveyed users, routes traffic through Google App Engine IP addresses also used by Gmail and Google Apps for Businesses. The GFW resorts to DNS poisoning of appspot.com domains rather than IP-blocking these shared addresses because a blanket IP block would disrupt commercially critical Google services — and GoAgent bypasses the poisoned DNS by connecting directly to the unblocked IPs, making surgical separation of circumvention traffic from business traffic infeasible.

Among 1,175 Chinese circumvention users surveyed in late 2012, purpose-built anti-censorship platforms showed severe attrition: Freegate had 44.3% former users but only 15.3% current users, while GoAgent and paid VPNs (piggybacking on commercially indispensable infrastructure) were the top two most-used tools in the past month. The median respondent had used four different types of circumvention tools, indicating frequent switching driven by blocking events.

§2 Tool Usage, Figure 2.1 evaluation

China's 2012 real-name registration law for consumer-facing online services (including VPNs) is designed to enable censors to segment circumvention-related consumer VPN traffic from business VPN traffic — permitting selective blocking of consumer VPNs while leaving corporate VPNs operational. The GFW had already demonstrated protocol-level VPN blocking capability; registration provides the identifying information needed to apply that capability selectively rather than as a blunt instrument.

§1 Introduction, §3 Collateral Freedom Matters policy

Tor, which has minimal commercial footprint and a distinctive network signature, was blocked throughout China using tailor-made GFW countermeasures and lost approximately 85% of its Chinese users as a result. In contrast to GoAgent and VPNs, China's censors can block Tor without significant economic collateral damage, making it uniquely vulnerable despite its strong privacy properties.

§2 Tool Usage, §3 Collateral Freedom Matters evaluation

In a survey of 1,175 Chinese circumvention users, reliability ranked as the top factor in tool selection (cited more often than speed), while privacy and trust in the developer ranked last. The overwhelming majority are versatility-first users seeking fast, reliable access to social media and search engines and are largely unconcerned about surveillance; only a small minority of journalists, dissidents, and activists are privacy-first users.

§2 Common Problems, Figures 2.3–2.4 evaluation

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

Article 19 documents that Iran combines technical filtering with formal coercion of major foreign platforms (including Telegram, Instagram, and WhatsApp) to comply with content removal orders under threat of full blocking. The report notes that Iran's 2022 Women Life Freedom protests accelerated platform blocking when foreign operators refused compliance, demonstrating that the censorship system operates in two modes: coerce-and-allow for compliant platforms, block for non-compliant ones. Domain fronting via these platforms is therefore subject to sudden revocation if political conditions change.

2026-article19-tightening-the-net §6 ip-blockingdns-poisoningthrottling

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

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.

2026-niere-dpyproxy-dns §6.3 dns-poisoningsni-blockingip-blocking