TSG's DNS parser enforces a hard limit of exactly 17 compression-pointer jumps per query; a query with 18 jumps causes domain name extraction to fail and suppresses the injection response. Only China's GFW Injector 2 shares the full combination of DNS flags 0x8180, compression-pointer encoding in injected answers, and the 17-pointer capability boundary, confirming it runs TSG's DNS injection code.

TSG's Context-Based Detector (CBD) evaluates circumvention tool signatures across JA3/JA4 TLS fingerprints, SSL certificate issuer fields, UDP payload length, first-packet byte patterns, server IP ranges, and FQDN matches, often combining multiple conditions with logical AND. Of 29 VPN and circumvention tool signatures logged in the VPN Signature File Update Log (March–November 2024), 21 carry risk level 5 (the maximum), indicating aggressive prioritization of blocking major tools including ExpressVPN, NordVPN, Tor Browser, and Psiphon.

§4.1, §4.1.2, Table 3, Table 4 detection

Measurements of TCP RST injectors confirm that GFW II and GFW III consistently yield a seed key k=13, matching TSG's default seed_key parameter in trick_algo_getrandval_with_seed. The probability of sharing TSG's default value of 13 by chance is approximately 10⁻⁴⁴, strongly indicating these GFW components run Geedge Networks TSG code or a close derivative.

§6.3, Table 7 deployment

Internal Jira tickets reveal that Psiphon lacked obvious protocol signatures, forcing censors to fall back to IP-based blocking of Psiphon3 client IPs combined with a 'whitelist protection mechanism' that allows traffic when the destination SNI matches a popular domain—an explicit collateral-damage tradeoff documented in the Confluence file 'GTN498 The collateral damage analysis of Psiphon3 Blocking.' A ticket from the Ethiopia (E21) deployment shows customers complaining that the VPN deny policy inadvertently blocked non-VPN applications.

§4.1.2, Figure 2, Figure 3 detection

TLS ClientHello length-field permutation tests show that GFW II's parsing behavior matches an older tagged version of TSG's SSL module, while Kazakhstan and Pakistan (DROP mode) exhibit parsing behaviors consistent with TSG QUIC plugin deployments. QUIC version fingerprinting further confirms Kazakhstan runs an older version of TSG's QUIC parsing code, and Myanmar's supported QUIC versions exactly match TSG's, spanning at least five countries confirmed or plausibly running TSG components.

§6.4, §6.5, Table 8, Table 9 deployment

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

Encrypted DNS has attractive anti-blocking properties for circumvention rendezvous, but its constraint of conveying only small amounts of data per message makes it difficult to use as a generic data-exchange channel. Fountain codes offer an uncomplicated way to transmit discrete, bounded-length messages over such channels, including those that are unordered or unreliable.

2026-cawthon-fountain-codes-censorship Abstract dns-poisoningdpi

TCP segmentation (splitting a DNS message into 20-byte TCP fragments) successfully circumvented DNS censorship in China for nearly all resolvers that support TCP. In Iran, TCP segmentation was only partially effective due to the censor's ability to reassemble TCP fragments when system load permits—some runs succeeded completely, others failed entirely across all resolvers. The "Last Response" mode (wait 3 seconds for the final UDP reply) was highly effective against China's on-path GFW injector for all resolvers except the fully IP-blocked Cloudflare 1.1.1.1 resolver. In China the technique worked for 40 of 41 tested resolvers.

2026-lange-towards §4.1, §6.2.1, §6.2.2 dns-poisoningdpi

As of June 2026, Iranian DPI blocking timescales are: CDN-fronted VLESS+WebSocket domains blocked within 24 hours; SSH dynamic port forwarding server IPs blocked within 8 hours; Reality and WireGuard connections blocked immediately (seconds) after handshake completion. This graduated timeline suggests separate fast-path (handshake-pattern) and slow-path (domain reputation / traffic accumulation) detection pipelines operating in parallel.

2026-pooribitwise-iran-advanced-dpi Issue body — combined observations dpisni-blockingip-blockingrst-injectiondns-poisoning

Of 6,915,266 domains extracted from the 572 GiB Geedge Networks Leak (GNL), 298,955 censored domains (93.7% of all GNL-censored domains) appear in neither Tranco top-1M nor CitizenLab test lists. Measurements across China (Guangzhou/Nanjing), Myanmar, Pakistan, and Algeria confirmed censorship via DNS injection and SNI-based TLS connection termination. The GNL covers 25–62% of Tranco-censored domains across countries, showing substantial but incomplete overlap. This vendor-side ground truth reveals a censorship surface roughly two orders of magnitude larger than curated academic test lists.

2026-sheffey-geedge §4.1, Table 2 dpisni-blockingdns-poisoningmeasurement-platform