GFW employs layered blocking for high-value targets: DNS poisoning for domains like google.com and wikipedia.org combined with null-routing of their hosting IPs, meaning packet-manipulation tools that operate at the TCP/HTTP layer (e.g., Geneva, DeResistor) cannot generate or test evasion strategies because no response is received to the initial SYN — the blocking occurs below the layer those tools target.

DeResistor-generated evasion strategies achieve an overall success rate of up to 98.61% against GFW (across vantage points in Qingdao, Shanghai, and Beijing) for the best strategy, and 100% in both India (Bangalore) and Kazakhstan (Oral) for the top-performing strategy, while standalone Geneva strategies tested in the same environment achieve comparable or slightly lower rates on some censors but are blocked at the IP level before training completes.

§6.3, Table 2 evaluation

DeResistor's two-objective fitness function (balancing evasion success and detection probability) reduces flow-level detection rates from 96.27% → 45.06% against China's GFW, 99.50% → 34.93% against India, and 99.50% → 49.22% against Kazakhstan over 5 training generations, while in all cases preventing TRW from reaching an IP-block decision that would terminate training.

§5.1, §6.2, Table 1 defense

Geneva packet-manipulation probing traffic exhibits distinctive features — corrupt data-offset fields, smaller packet sizes, overlapping TCP segments, TTL variance, and non-zero SYN packets — that allow simple ML classifiers (Decision Trees, Random Forests, Logistic Regression, SVM) to detect it with AUC > 0.99. A subsequent TRW-based IP-level detector can then block the source IP with high confidence after inspecting only 2 Geneva probing flows.

§4.1–§4.2 detection

Interleaving a single normal benign flow (jump size J=1) after each detected probe prevents the TRW likelihood ratio from converging to the IP-block threshold across all 11 simulated censors and all three real-world censors tested; setting J>1 risks triggering a history-aware TRW reset that can paradoxically accelerate IP-level detection.

§5.2, §6.2 defense

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