Because a disproportionate number of Tor exit nodes are located in the EU, GDPR-motivated blanket blocking of EU IP ranges creates collateral access restrictions for Tor users globally. This illustrates that privacy-protective legislation and censorship-circumvention infrastructure can have directly competing effects when server-side enforcement is implemented via coarse geographic IP filtering.

Across 85,421 Cloudflare-hosted domains crawled from five vantage points, 524 websites employed country-based blocking (Cloudflare error 1009). Ukraine (VPN) received 313 geo-blocks while Scotland (same VPN provider) received only 175, suggesting that IP/ASN reputation or exit-node characteristics cause significant variation in observed blocking rates even when controlling for the access method.

§4, Table 2 evaluation

After GDPR took effect on May 25, 2018, 74 websites that had previously served all three EU vantage points (London, Sofia, Frankfurt) began blocking them; 40 returned explicit 'Blocked due to GDPR' blockpages with HTTP 403, 7 used HTTP 451 Unavailable For Legal Reasons, and all 47 sites with explicit blockpages were local news outlets.

§6, Table 3 evaluation

Ukraine and Scotland both used the same VPN provider yet Ukraine received 1,874 CAPTCHA challenges vs. 309 for Scotland, and 1,519 browser verification challenges vs. 1,091 — a roughly 6× and 1.4× difference respectively. Only Ukraine was flagged as a VPN or Tor node by OctoNet's HTTP filter, indicating that IP/ASN reputation drives security-motivated blocking independently of the transport protocol used.

§5, Table 2 detection

The paper enumerates at least eight distinct non-censorship motivations for server-side geo-blocking — economic sanctions, third-party liability (SESTA), copyright, GDPR compliance, security/fraud concerns, hosting costs, revenue optimization, and misconfiguration — each of which can produce the same observable signals (403 blockpages, DNS failures, TCP resets) as government censorship. Naive measurement methods that treat all location-based unavailability as censorship will produce systematic false positives.

§2, Table 1 policy

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