asn-blackholing   ASN / prefix blackholing

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 deployment

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 policy

AS-targeted shutdowns — where censors restrict connectivity at specific ISPs or autonomous systems rather than imposing country-wide outages — evade country-level aggregation in automated detection systems, which are calibrated to detect national-scope disruptions.

2026-cheek-gaps-record-observability §3 Detection Gap Categories evaluation

The dominant enforcement mechanism in April 2026 was administrative 'reporting + line-cutting' (通报 + 拔线) backed by MIIT bulletins, not protocol-level DPI changes. Operators reported that newly acquired upstream resources were reported to authorities quickly after acquisition, recovery timelines were uncontrollable, and some upstream providers refused refunds after enforcement actions, producing sustained capacity contraction across the shared VPN-reseller ecosystem.

2026-ermao-april-airport-outage §这轮波动到底发生了什么 deployment

The April 2026 enforcement cycle created a resource-scarcity feedback loop: upstream providers cut lines with no obligation to refund resellers, newly acquired replacement resources can themselves be reported and cut within days, and stable-resource availability windows are described as "越来越短" (increasingly short) while costs rise concurrently. The overall effect is systemic capacity contraction forecast to continue through at least May 2026.

2026-ermao-april-airport-outage §这轮波动到底发生了什么 / §四月后的趋势判断 deployment

Transit/relay architectures (国内入口 + 海外转发) suffered disproportionate impact because multiple nodes share a single domestic entry point: when that entry is reported or cut, the entire batch of nodes fails simultaneously. Operators described this as "三线变单线" (three-line to single-line collapse), with only direct-connect fallback remaining — at higher latency and with worse peak-hour performance.

2026-ermao-april-airport-outage §为什么中转机场这次受冲击更明显 evaluation

IODA data confirmed the February 28, 2026 Iran shutdown was implemented via BGP route withdrawals and collapse of IP-space announcements, not merely application-layer blocking — the underlying routing infrastructure itself was withdrawn.

2026-gusgustavo-iran-internet-shutdown Issue body (IODA reference) deployment

CensorLess's threat model explicitly relies on a rational-censor assumption: the censor will not block entire cloud-provider IP ranges or domain namespaces because the collateral damage to legitimate business services would be politically and economically unacceptable. AWS Lambda's inherent IP-address ephemerality (new IPs on each invocation, function lifetime up to 15 minutes) means even censors willing to attempt enumeration face a continuously shifting target distributed across the cloud provider's global address space.

2026-kang-censorless-serverless §4.2 defense

Country-level analysis shows significant sensitivity of AS-level transit dependency to the distribution of relay capacity across ASes within each country, implying that a censor controlling a dominant national transit AS gains disproportionately high visibility into Tor traffic if domestic relay capacity is concentrated in that AS's customer cone.

2026-wang-who-carries-tor Abstract evaluation

SURF (AS1103) surged to over 50% exit hegemony in 2024, meaning a single AS gained visibility into the majority of bandwidth-weighted Tor exit traffic. This represents a dramatic concentration event in an otherwise persistent but distributed chokepoint landscape spanning 2015–2025.

2026-wang-who-carries-tor Abstract evaluation

A longitudinal study of Tor transit dependency from 2015 to 2025 reveals persistent concentration in a small number of transit ASes, indicating that AS-level chokepoints enabling flow-correlation attacks are a structural rather than transient property of the Tor network.

2026-wang-who-carries-tor Abstract evaluation

The June 2025 Iran shutdown lasted 10 days (June 17–26) and generated real-time community measurement via IODA and crowdsourced circumvention testing, establishing this event as primary-source documentation of simultaneous carrier-level BGP suppression and application-layer proxy blocking—a dual-layer shutdown strategy distinct from typical content-level filtering.

2025-pirooz-gthb-internet-completely-blocked Issue metadata / abstract evaluation

Iran implemented a near-complete internet shutdown from June 17–26, 2025 using selective IP-based whitelisting: api.github.com and api.google.com remained accessible while the general internet was blocked. IODA measurements confirmed that ASes 44244 (IranCell) and 57218 (RighTel)—the two largest mobile carriers—were nearly unreachable for the duration.

2025-pirooz-gthb-internet-completely-blocked Issue body / abstract deployment

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 defense

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 detection

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 deployment

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 evaluation

Seven years of Roskomnadzor blocklist history (Nov 2012–April 2019) show the list grew to 132,798 unique domains and 324,695 unique IPs, with a dramatic spike in 2018 when Russia blocked Telegram by adding subnets covering approximately 16 million IP addresses—producing major collateral damage to co-hosted Google and Amazon services and illustrating that subnet-level blocking is the blunt instrument of last resort for CDN-hosted targets.

2020-ramesh-decentralized §VI-A, §II-B evaluation

If China attempts the Routing-Around-Decoys (RAD) attack by blackholing paths that transit the 30 key ASes, 92.25% of all paths transiting Chinese ASes (306,874 of 332,742) originate at ASes outside China, making such filtering self-defeating through severe collateral damage to foreign transit customers. The 30 key ASes cover 98.8% of paths from Chinese ASes to globally popular destinations and at least 80% for nearly all adversary countries studied.

2017-gosain-devil-s §6.2, Figure 7, Figure 9 defense

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.

2016-singh-politics §1, §5 detection

Both Egypt and Libya demonstrate that concentration of Internet infrastructure under state ownership—in Egypt, all submarine fiber backhaul terminated at a single facility, the Ramses Exchange, controlled by the state telecommunications provider—makes country-wide BGP-based shutdowns technically straightforward. The authors conclude that the small number of state-controlled parties involved in international connectivity was the critical enabling factor, not any novel technical capability.

2011-dainotti-analysis §5.1.1 policy

Unsolicited background radiation traffic to the UCSD network telescope—particularly Conficker worm scanning (TCP SYN, port 445, 48-byte packets)—dropped nearly simultaneously with Egyptian BGP route withdrawals on January 27, corroborating control-plane analysis with data-plane evidence. Crucially, some worm-infected hosts continued to generate outbound scanning traffic even after their prefixes were BGP-withdrawn, because packet filtering was absent; this asymmetry between inbound unreachability and outbound connectivity can distinguish pure BGP-based blocking from combined BGP-plus-filtering approaches.

2011-dainotti-analysis §4.3, §5.1 evaluation

Egypt's Internet shutdown on January 27, 2011 was accomplished via BGP route withdrawals: approximately 2,500 IPv4 prefixes (out of 2,928 visible) disappeared within a 20-minute window beginning at 22:12:26 GMT, leaving only 176 prefixes visible by 23:30:00 GMT. The shutdown lasted more than five days, with BGP connectivity beginning to return at 09:29:31 GMT on February 2, and more than 2,500 Egyptian prefixes back in global BGP tables by 09:56:11 GMT.

2011-dainotti-analysis §5.1.1, §5.1.2 evaluation

During Egypt's 5.5-day Internet blackout, active CAIDA Ark measurements found that only 1% of probes to Egyptian IPv4 prefixes received responses, compared to 16–17% on normal days. The minority of addresses that retained bidirectional connectivity all mapped to BGP prefixes that had not been withdrawn—including prefixes serving the Egyptian stock exchange and two national banks, whose 83 prefixes were kept live until January 31 at 20:46:48 GMT before being simultaneously withdrawn.

2011-dainotti-analysis §5.1.2 evaluation

Libya implemented escalating Internet disruptions before executing a sustained blackout: a 6.8-hour curfew on February 18 and an 8.3-hour curfew on February 19, followed by a 3.7-day near-total blackout beginning March 3. The authors detected what they believe were Libya's attempts to test firewall-based packet filtering before transitioning to more aggressive BGP-based disconnection, demonstrating a two-phase escalation pattern.

2011-dainotti-analysis §1, §5.2 evaluation

Cloud-based onion routing confronts censors with a collateral-damage dilemma: blocking a cloud provider's IP prefixes requires blocking all co-hosted services (Amazon EC2 hosted over 1 million instances sharing common IP prefixes in 2010), while allowing the traffic means circumvention succeeds. Rotating IP addresses—by retiring and spinning up new VM instances or via DHCP/gratuitous ARPs—reduces the window a blocked address remains in service, forcing censors into a perpetual cat-and-mouse game across all major cloud providers simultaneously.

2011-jones-hiding §2.3 defense

China has only 3 points of control covering approximately 240 million IP addresses (roughly 80 million IPs per point of control), the lowest ratio among large-population countries. This enabled China to cut off nearly all Internet access for the Xinjiang region for ten months beginning July 2009.

2011-roberts-mapping §II, §VI deployment

Eastern Asia averages 4.80 points of control and a complexity score of 1.54 across 510 million IP addresses, while Eastern Europe averages 19.10 PoC and a complexity score of 11.35 across 74 million IPs — nearly twice the complexity of any other region. Russia specifically has 2,346 autonomous systems and a complexity score of 19.39, versus China's 177 ASes and score of 0.11.

2011-roberts-mapping §II, Table II, Table III evaluation

By 2009, the top 150 autonomous systems carried approximately 50% of all Internet traffic globally, up from roughly 30% in 2007. Akamai alone claimed approximately 20% of all web traffic, and the proposed Level 3 / Global Crossing merger would have covered over half the world's IP addresses.

2011-roberts-mapping §I evaluation

Iran and Libya each have a single point of control (1 AS), making complete national internet shutdown achievable with a single administrative action. Egypt's 2011 shutdown left one AS (Noor Group, 4.9% of connected IPs) operational for four days, apparently due to its role serving the Egyptian stock exchange and other core financial institutions.

2011-roberts-mapping §VI, Figure 7 deployment