DNS hijacking of blocked gambling domains in Greece also destroyed MX records for those domains in seven of eight ISPs, making it impossible for users to send email to the censored companies. Only OTE preserved MX records for some (not all) blacklisted domains, and even those were not consistently updated. The Greek Gaming Commission's own public guidance directed affected users to consult prior bank statements for contact information.

After the EEEP blacklist was updated in July 2014 to remove pokerstarsblog.com, multiple ISPs continued blocking it — overblocking was observed at Cosmote (7 entries), Wind (7 entries), Vodafone (7 entries), Cyta (3 entries), Forthnet (3 entries), HOL (3 entries), and OTE (3 entries). The blacklist itself contained 28 duplicate domains (6.39%), 17 malformed entries (3.88%), and 3 entries (0.68%) with no gambling content (expired or parked domains).

§5.2, Table 4 evaluation

At least two ISPs (Cyta and Wind) returned fake HTTP 404 errors instead of mandated block pages for a portion of censored entries, and some ISPs served connection timeouts (port 443 blocked) with no explanation — in both cases obscuring deliberate censorship as an apparent network or server failure. Additionally, Cyta embedded Google Analytics on its block landing page to track users who attempted to access censored content.

§4.2, §5.2 policy

Across eight Greek ISPs measured in June–August 2014, DNS hijacking was the dominant blocking method: seven of eight ISPs used it exclusively, while only Vodafone deployed DPI (Bluecoat WebProxy/6.0) for URL-level filtering. Compliance with the EEEP blacklist of 438 entries ranged from 21.91% (Forthnet) to 100% (Cosmote, HOL, OTE), with no ISP exactly matching the regulator's list.

§4.2, Table 1 evaluation

Vodafone Greece's DPI system (Bluecoat WebProxy/6.0) performed exact-URL matching against the EEEP blacklist: requests to rivernilecasino.net and www.rivernilecasino.net passed through unblocked, while the exact blacklisted URL www.rivernilecasino.net/index.asp was intercepted and redirected to http://1.2.3.50/ups/no_access_gambling.htm. Subdomains of DNS-hijacked domains returned NXDOMAIN with no A record, making them silently unreachable rather than redirected.

§4.2, Appendix A.1 detection

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

Both Firefox and Chromium leak cleartext DNS before establishing encrypted DNS connections: they first send an unencrypted UDP DNS query to resolve the DoH server's domain (e.g., doh.opendns.com). An in-path censor can intercept and poison this initial query, making encrypted DNS in browsers completely ineffective without additional circumvention of the resolver-lookup step. Additionally, Chromium always includes the SNI extension in the encrypted DNS TLS handshake (e.g., "doh.opendns.com"), leaking the resolver identity even after the initial lookup. No resolver requires SNI to be present for certificate validation when the resolver's IP certificate is configured.

2026-lange-towards §2.4, §7, §10 dns-poisoningsni-blocking

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