Ad server domains are structurally immune to censor blocking due to collateral-damage risk: Google DoubleClick is embedded in 1,843,854 publisher sites and PubMatic in 215,046, making IP-blocking of these domains prohibitively costly for any censor. Measurements of Alexa top-10K confirm the top 20 ad servers handle more than 75.6% of all ad requests.

82.2% of ad requests from Alexa top-500 websites are sent over HTTPS (Table 2), encrypting the HTTP Referer field. This prevents censors from correlating a user's direct-path ad request back to a censored publisher domain in the vast majority of cases; only the remaining 17.8% of HTTP ad requests are vulnerable to Referer-based traffic analysis.

§4.3, Table 2 evaluation

Relay-based circumvention severely degrades ad relevance: across Alexa top-500 uncensored sites, the overlap between ad sets fetched via Tor and the direct-path ground truth averaged only 28%, with near-zero overlap for sites serving geo-targeted ads. For blocked sites, only ~16% of ads shown via Tor were in the user's language.

§3.2, Table 3 evaluation

ADVENTION's split-path design — fetching publisher content via relay and ad requests via the direct path — raises average ad-set overlap from 28% (Tor) to 70%; combining ADVENTION with Intelligent Relay Selection (language-matched relay) further increases average overlap to ~80%. For blocked sites, ADVENTION with IRS raised ad relevance from ~16% to 100%.

§5.1, §5.3, §5.4 evaluation

ADVENTION provides up to 47% improvement in average page load time (PLT) compared to Tor, because ad requests — which are often on the critical rendering path — are served over the direct channel rather than through the relay. The exact improvement depends on webpage structure and bottleneck resources.

§5.1, Figure 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

Brussee measures a systematic pattern of Chinese government websites actively blocking access from outside China (the "reverse Great Firewall"), publishing a CSV dataset of affected domains (available at zenodo.org/records/18172145). The paper frames this outbound geo-blocking as a cybersecurity-motivated practice — Chinese authorities classify foreign access to domestic government infrastructure as an attack surface — distinct from the inbound information control goal of the GFW.

2026-brussee-reverse-great-firewall §3, §5 ip-blockingasn-blackholing

Brussee develops a conceptual framework distinguishing two logics of government geo-blocking: (1) information control (blocking inbound foreign content from domestic users) and (2) data sovereignty / attack-surface reduction (blocking outbound access by foreign actors to domestic systems). Chinese government site blocking of external IPs is motivated primarily by the second logic, creating an asymmetric internet topology where CN citizens cannot reach the outside world, and outside actors cannot probe CN government infrastructure.

2026-brussee-reverse-great-firewall §2, §4 ip-blockingasn-blackholing

ShieldShare demonstrates that an Android application can route all hotspot-client traffic through a VPN tunnel without root access by using a SOCKS5/HTTP/HTTPS proxy layer between the hotspot and the VPN, with per-client traffic accounting and quota management. The system works because Android's native hotspot does not forward VPN routing tables to connected clients; ShieldShare interposes a proxy that handles this. Released as open-source.

2026-edorh-shieldshare §Abstract ip-blocking