Because CovertCast clients connect to live-streaming service infrastructure (e.g., YouTube servers) rather than to CovertCast servers directly, IP-address blacklisting of CovertCast infrastructure does not allow censors to identify or disrupt client connections. Discovering the CovertCast server's IP address is therefore irrelevant to the censor's blocking goal.

CovertCast's broadcast model decouples server workload from client count: one server can serve unlimited simultaneous clients without per-connection overhead, unlike hide-within systems such as FreeWave where server costs grow linearly with users. This architecture also defeats Sybil-based DoS attacks, because flooding the server with fake client requests does not increase server load — the server never processes individual client connections.

§2, §7.2 defense

Under degraded network conditions, CovertCast page load times increased by 2–3× at 800 Kbps (below YouTube's minimum 720p bitrate of 1.5 Mbps), with 20 of over 4,000 images dropped at 800 Kbps; at 10% packet loss, 35 images were missed due to YouTube temporarily accelerating video playback; at 20% packet loss, 720p video could not be loaded at all.

§6.4, Fig. 6, Fig. 7 evaluation

A KL-divergence classifier trained to distinguish CovertCast streams from real YouTube streams achieved only 33–45% true positive rate on packet-size distributions and 36–41% on inter-packet timing distributions — below random guessing — while maintaining 86–98% true negative rates. Overall classifier accuracy was approximately 65–68%, driven entirely by the high true negative rate rather than genuine detection capability.

§7.5, Table 1 evaluation

CovertCast uses the identical video codecs, streaming protocols (RTMP/HTTPS), and server endpoints as any other YouTube live stream, making it indistinguishable from regular streaming traffic to both passive protocol-analysis and active traffic-manipulation attacks. Any active attack that disrupts CovertCast connections — such as selective packet dropping — would equally disrupt all non-circumvention viewers of the same streaming service, imposing prohibitive collateral damage.

§7.4, §7.5, §7.6 defense

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