China actively censors websites far outside the popular-traffic tier: many discovered censored domains appear in the tail of the Alexa Top 1,000,000, and some are absent from Alexa entirely. This demonstrates the GFW pursues content-classified hosts regardless of traffic rank, not only high-visibility platforms.

The 1,125 newly discovered censored domains span a broad taxonomy: Chinese human rights organizations, Tibetan rights outlets, Falun Gong and religious freedom sites, minority news, privacy-enhancing technology providers, and sources covering Tiananmen and the 1989 democracy movement—none appearing on the Alexa Top 1,000 or FilteredWeb's blocklist. Privacy-enhancing technology providers appear explicitly as a censored category alongside political and religious content.

§1, §5.1, §6 detection

Multi-word Chinese phrases as search seeds discover qualitatively different censored sites than individual English words: the phrase 'Chinese human rights violation' surfaces Chinese activist homepages and culture-specific outlets, while individual constituent words return only well-known Western media. TF-IDF scoring against a Chinese corpus ranks culturally rare phrases (e.g., '自由亚洲电台' / Radio Free Asia) as high-signal seeds and discards common filler phrases.

§3.1–3.2 evaluation

Using NLP phrase extraction on Chinese-language censored pages, the system discovered 1,125 new censored domains not present on any publicly available blocklist, producing a list 12.5× larger than the standard Citizen Lab list (220 web pages, 85 domains). Across three evaluations (unigrams, bigrams, trigrams, each capped at 1,000,000 URLs), only 3 of the top 50 discovered domains overlapped with FilteredWeb's top 50.

§5.1, Table 1 evaluation

Culturally specific Chinese phrases are strong predictors of censorship: unigrams for controversial figures—Wang Qishan (74%), Li Hongzhi (64%), Guo Boxiong (62%), Hu Jintao (56%)—returned the highest block rates. Trigrams such as 'Beidaihe meeting' (54%), 'CCP's religious policy' (42%), and 'Tiananmen Square demonstrations' (32%) showed similar patterns, confirming King et al.'s finding that references to collective political dissent are disproportionately targeted.

§5.3, Tables 2–4 detection

IRBlock discovered that 1.7M of 3.3M blocked apex domains (52%) were attributed to blanket suffix-level blocking rules rather than individual domain listings. Examples include regex patterns targeting all Israeli domains (.il TLD), adult content (.porn), and country-coded suffixes (.com.mx, .my.id). Of 87K Tranco-ranked apex domains analyzed, 37% fell into adult content, with entertainment and gambling following. Approximately 1.27M apex domains were jointly censored by both DNS and HTTP filters, while the two filters maintained operationally independent blocklists for a significant fraction of domains.

2025-tai-irblock §5.3 dns-poisoningip-blockingkeyword-filtering

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.

2024-gosain-out §4.3, §5 ip-blockingkeyword-filtering

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.

2024-gosain-out §4.3 (Permanent ban subsection), Table 2 ip-blockingkeyword-filtering

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.

2024-gosain-out §4.3 ip-blockingkeyword-filtering

GFWeb tested 1.02 billion domains against the GFW over 20 months and discovered 943,000 pay-level domains blocked by HTTP filters and 55,000 by HTTPS filters — the largest GFW blocklist dataset ever published. The HTTP-to-HTTPS ratio (17:1) confirms that the GFW's HTTPS keyword-based and SNI-based blocking covers far fewer domains than its HTTP host-header blocking, likely because HTTPS blocks carry higher collateral-damage risk.

2024-hoang-gfweb Abstract, §5.1 dpidns-poisoningip-blockingkeyword-filteringsni-blocking

The largest measurement study of Turkmenistan censorship to date tested 15.5 million domains and found more than 122,000 domains censored using separate blocklists for DNS, HTTP, and HTTPS. Reverse-engineering the blocking rules revealed approximately 6,000 over-blocking rules that cause incidental filtering of more than 5.4 million additional domains — a 44x collateral damage ratio relative to intentionally blocked domains.

2023-nourin-measuring §Results dns-poisoningdpikeyword-filteringip-blocking