Iran's national policy forces all domestic ASes to route through a single national telecom AS (AS 12880), resulting in Iran connecting to only 6 international networks. By contrast, Singapore has 257 domestic ASes connected to 3,022 international ASes despite similar geographic scale.

Domestic mesh traceroutes (both source and destination inside the target country) uncovered 5,562 new AS edges not present in standard BGP table–derived topology datasets, far exceeding the 647 new edges found by inside-out/outside-in traceroutes using up to 25 probes. Russia, the US, France, the UK, and Ukraine gained the most new edges.

§2.2, Table 1 evaluation

A decision tree with linear regression at leaves (DTLR) trained on AS-topology features for 168 countries predicts Freedom House freedom category (Free/Partly Free/Not Free) with 95% accuracy. Average FPI prediction error was 3.47%, and prediction error remained ≤8 points (on a 0–100 scale) 90% of the time under leave-one-out cross-validation.

§3.3 evaluation

IP density (number of IP addresses per person) is the single most predictive feature of a country's Freedom of Press Index. A normalized IP density value of ≥0.167 reliably predicts high freedom of expression, while normalized maximum BGP policy-compliant path length ≥0.643 reliably predicts low freedom.

§4, Figure 2 evaluation

Singapore's AS topology — 257 domestic ASes with 3,022 international connections — resembles that of high-freedom countries, yet its Freedom of Press Index is 33 (Partly Free), making it a structural outlier where rich international BGP connectivity coexists with enforced information controls. Our DTLR model predicts Singapore's FPI should be ≥70 (Free).

§5 evaluation

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

NetShuffle targets edge networks — small autonomous systems and entities that obtain IP address blocks from upstream providers — as a new class of support base for circumvention infrastructure. This class has received scant attention from prior work, which has focused on cloud providers and volunteer desktop machines. Edge networks represent a large pool of diverse IP space that is harder to block via ASN blackholing compared to a small number of major cloud providers.

2024-kon-netshuffle §1, §2 ip-blockingasn-blackholing

On March 28, 2022, Russian ISP RTComm (AS8342) hijacked Twitter's IPv4 prefix 104.244.42.0/24 for approximately 45 minutes (12:05–12:50 UTC) and announced it to the global Internet as a blocking measure. The hijack was blunted because Twitter had preemptively registered RPKI route origin authorizations (ROAs) for its prefixes, causing RPKI-validating ASes worldwide to reject the hijacked route.

2023-ramesh-network §4.3 bgp-hijackasn-blackholing

Documented Internet shutdown events grew from 75 in 2016 to 213 in 2019 across 33 countries, with individual shutdowns lasting from hours to 472 days (Chad). These shutdowns completely sever IP connectivity, rendering all existing circumvention tools (Tor, VPNs, Shadowsocks, etc.) non-functional since they require at least partial Internet access to operate.

2023-sharma-dolphin §1–2 asn-blackholingip-blocking

27 of 80 tested VPN providers had servers within a single AS (AS 9009, M247 Ltd), and VPNalyzer identified 14 providers sharing 4 specific IP blocks within that AS; 2 additional providers shared an IP block in AS 60068 (Datacamp). Such infrastructure concentration enables censors to block multiple VPN products simultaneously with a single IP-range or AS-level rule.

2022-ramesh-vpnalyzer §VI-D ip-blockingasn-blackholing