In the Clouds P2P protocol, a blocking attack against a specific topic requires adversaries to occupy at least 50% of the 200-peer region closest to the resource provider to be effective; below that threshold, query messages routed through multiple paths bypass the censorship. This 50% threshold holds regardless of the number of clouds κ created per peer.

The number of clouds per peer κ has no measurable effect on censorship resistance (Figure 5 curves are identical across κ = 1–4), while cloud size is the dominant driver of message overhead. This decoupling means designers can increase κ to improve anonymity without degrading censorship resistance or incurring bandwidth cost.

§5.4–§5.5 defense

Cloud locality — building clouds from semantically close peers via short-distance links — ensures that 2-wise and 3-wise cloud intersections have median cardinality between 40 and 50 peers, and the probability that a peer participates in clouds whose pairwise intersection falls below 40 is below 10⁻⁴, rendering intersection attacks infeasible in practice.

§5.3 defense

The surrounding attack on peer anonymity is also effective only when adversaries control at least 50% of the ~100 semantically closest peers to the target; at 25% malicious peers, at least 10 honest peers still join the target's cloud at every step of the joining algorithm, preserving k-anonymity.

§5.2 evaluation

The Clouds protocol retrieves approximately 70% of available answers even in the absence of attackers, representing a ~30% retrieval performance decrease relative to an insecure SON. This baseline loss stems from the cloud-based routing mechanism's probabilistic message delivery, not from adversarial interference.

§5.6 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