India's app-filtering architecture is three-tiered: 136/220 apps (Tier 3) are inaccessible only via official app stores and trivially accessible after sideloading; 23 apps (Tier 2) additionally enforce IP geo-blocking; and 7 apps (Tier 1) combine IP geo-blocking with SIM-based locale detection. One outlier, ChessRush, restricted content at CDN edge servers serving Indian users, requiring both a foreign source IP and a foreign CDN edge server (via foreign DNS resolver) to bypass.

For Tier 2 apps (IP geo-blocking only), using a VPN with a foreign endpoint was sufficient to restore access. For Tier 1 apps (SIM + IP geo-blocking), the authors confirmed that (1) removing the Indian SIM card and accessing via WiFi, or (2) intercepting HTTP traffic with a MITM proxy to suppress or rewrite the carrier_region=IN parameter, fully bypassed server-side censorship. The authors note that Indian users primarily rely on mobile Internet, making SIM removal impractical as a user-facing solution.

§4.3, §5 defense

Across four major Indian ISPs (Reliance Jio, Airtel, Vodafone-Idea, and ACT) cumulatively serving more than 95% of Indian clients, the authors found zero network-level interference with 220 banned Chinese apps. DNS resolved to legitimate addresses, TCP and TLS handshakes completed successfully with actual app servers, and responses were served directly by app publishers — not by ISP middleboxes.

§4.2 evaluation

After India imposed a permanent ban in January 2021, seven of the eight previously SIM-only-blocked apps escalated to dual-factor filtering: they continued extracting carrier_region=IN from the SIM card while simultaneously adding IP geo-blocking. Accessing these apps now requires both a VPN (for source IP masking) and SIM removal or carrier_region parameter suppression; MICO Chat remained the sole app using only SIM-based blocking.

§4.3 (Permanent ban subsection), Table 2 evaluation

Seven of the 220 banned apps (Tier 1, including TikTok, Likee, Kwai, UC Browser, FaceU, Hago, and V-Fly) used the Android TelephonyManager.getSimCountryISO() API to read the primary SIM's country code and embed a carrier_region=IN parameter in HTTP requests, enabling server-side identification and blocking of Indian users regardless of source IP or VPN state. A dual-SIM phone with an Indian SIM in the secondary slot only (primary empty or non-Indian) bypassed the check.

§4.3 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

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