The paper demonstrates that two protocol-specific censorship changes — QUIC blocking reaching 100% and DNS-over-TCP blocking reaching 96.68% — both occurred in the scan conducted immediately before Iran's June 18 full blackout, and that similar shutdown preparations were also documented before Iran's January 2026 shutdown. The authors hypothesize that continuous long-term measurement of protocol-specific censorship rates could provide advance warning of impending shutdowns before they come into full effect.

HTTP censorship blockpages in Iran fell into two distinct clusters distinguished by IP TTL values: type NTL1 (TTL 53–55) and type NTE1 (TTL 186–188); TCP RST injections targeting TLS and DNS-over-TCP exhibited the same two TTL ranges. The NTL1 injector was absent on June 11 but present on other days, leading the authors to conclude that an entire injector went offline rather than that a single injection pattern was selectively disabled.

§2.2.5 detection

After the shutdown lifted (Scan 3), DNS-over-UDP degraded severely — 89.18% of the 9,000 queried domains were affected — but the paper attributes this to general UDP transport instability rather than domain-specific censorship, corroborated by GitHub user reports of ongoing UDP issues. TCP-based protocols (HTTP, TLS) returned to pre-shutdown censorship levels (~15%) in Scan 3, confirming the post-shutdown persistence effect was UDP-specific and not a broadening of the blocklist.

§2.2.4, Table 1 evaluation

In the pre-shutdown scan (Scan 2), Iran's QUIC censorship jumped from 1 domain (0.01%) to 9,000 domains (100%) via complete UDP Initial-packet drops, while DNS-over-TCP censorship spiked from 15.12% to 96.68% of 9,000 queried domains. Both changes preceded the full blackout by roughly 5 days, indicating they were preparatory measures rather than incidental. After the shutdown lifted, QUIC remained 100% blocked while DNS-over-TCP returned to baseline (15.38%).

§2.2, Table 1 evaluation

Iran's June 2025 shutdown was enforced using fine-grained, service-level techniques rather than BGP withdrawals or a single 'big switch' event: individual protocols were selectively blocked before and after the 7-day full blackout (June 18–25), with the total preparation and recovery periods each lasting roughly 4–5 days. Cloudflare Radar showed HTTP traffic reaching near-zero by June 18 but partial recovery already on June 21, while the authors' vantage point (AS57497) remained unreachable until June 25, confirming heterogeneous recovery across Iranian networks.

§2, §3 deployment

A compiled blocklist dataset documents 43,083 apex domains blocked via DNS filtering across 6 Indian ISPs, representing one of the largest systematic inventories of Indian DNS censorship scope published to date.

2026-qurbat-list-domains-blocked compiled_blocklist.csv (main dataset) dns-poisoningmeasurement-platform

The dataset incorporates Tranco popularity rankings for blocked domains (derived from the 'Poisoned Wells' research), enabling measurement of how DNS blocking in India intersects with high-traffic websites rather than being confined to obscure domains.

2026-qurbat-list-domains-blocked Abstract (Tranco ranking annotation) dns-poisoningmeasurement-platform

The blocklist spans 6 distinct Indian ISPs, enabling cross-ISP consistency analysis; the multi-ISP scope reflects that DNS-based blocking in India is implemented heterogeneously at the ISP level rather than via a single national chokepoint.

2026-qurbat-list-domains-blocked Abstract / dataset metadata dns-poisoningmeasurement-platform

Of 6,915,266 domains extracted from the 572 GiB Geedge Networks Leak (GNL), 298,955 censored domains (93.7% of all GNL-censored domains) appear in neither Tranco top-1M nor CitizenLab test lists. Measurements across China (Guangzhou/Nanjing), Myanmar, Pakistan, and Algeria confirmed censorship via DNS injection and SNI-based TLS connection termination. The GNL covers 25–62% of Tranco-censored domains across countries, showing substantial but incomplete overlap. This vendor-side ground truth reveals a censorship surface roughly two orders of magnitude larger than curated academic test lists.

2026-sheffey-geedge §4.1, Table 2 dpisni-blockingdns-poisoningmeasurement-platform

Neither China nor Iran directly block ECH ClientHello messages; instead both effectively prevent ECH by censoring encrypted DNS resolvers. China blocks Cloudflare's DoH/DoT resolver (mozilla.cloudflare-dns.com) via SNI-based blocking in TLS and QUIC, causing residual censorship of up to 360 and 180 seconds respectively. Iran blocks both Cloudflare and NextDNS DoH hostnames via DNS block-page injection, TLS TCP RST, and HTTP block pages. Iran cannot analyze QUIC, so DoQ is uncensored and enables ECH in Iran. China's NextDNS IP blackholing affected only one of two resolved IPs, leaving an uncensored path.

2025-niere-encrypted §5, Table 1, Figure 5 dns-poisoningsni-blockingrst-injectionhttp3-quic-block

Censorship enforcement varies dramatically across Iranian ASes. AS58224 (TCI, 3.6M IPs) blocks 89-98% of IPs across DNS injectors and 87.6% for UDP. AS197207 (MCCI, 2.3M IPs) and AS44244 (IranCell, 1.3M IPs) show near-zero censorship (0.15-0.76% across injectors). AS31549 (RASANA, 577k IPs) blocks 97-99% for DNS/HTTP but 64% for UDP. Some IPs— including those belonging to the Iranian President's website and Ministry of Foreign Affairs—are deliberately exempted from bidirectional censorship. Two exempted MFA IPs (109.201.19.184 and 109.201.27.67) appear linked to APT15 (Playful Taurus) C&C infrastructure.

2025-tai-irblock §5.1, §5.2, Table 1 dns-poisoninghttp3-quic-blockip-blocking