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.

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

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.

§6.1, Table 5 deployment

Testing the Tranco Top 100k domain list from Russian vantage points shows that all 2,644 domains blocked over TLS SNI are also blocked over QUIC SNI, and domains accessible via TLS are accessible via QUIC—indicating the TSPU maintains a unified SNI blocklist across protocols. Additionally, 31 domain patterns including discord.com exhibit 'residual clearance': QUIC connections to those domains are not censored when immediately preceded by non-censored data on the same 4-tuple; 22 domains are only blocked on port 443.

2026-heitmann-russia-s-early-introduction §3, Table 3 sni-blockinghttp3-quic-blockdpi

Reproducing Zohaib et al.'s 10-payload QUIC parser test suite against Russian TSPU devices reveals that the Russian QUIC parser differs meaningfully from the GFW: payload 8 (PING and PADDING frames inserted before the Crypto frame), which circumvents the GFW, does not bypass Russian censorship. Payload 10 (QUICv2) bypasses both censors. Payload 9 (ECH with outer SNI cloudflare-ech.com) is blocked by Russia; payload 3 (version bytes 0x00000002 with invalid MAC) is blocked by both.

2026-heitmann-russia-s-early-introduction Appendix B, Table 2 http3-quic-blockdpisni-blocking

As measured from three Russian vantage points in March–April 2026, TSPU devices decrypt QUIC Initial packets, locate the SNI extension in the embedded TLS handshake, and drop packets with forbidden domains plus all subsequent packets on the 4-tuple for 420 seconds (timer resets on each packet). Censorship is unidirectional (outgoing only), covers all destination ports up to 65535 at Saint Petersburg and Novosibirsk (Moscow exempts 22% of system ports 1–1023), and targets only QUICv1—QUICv2 passes uncensored at all vantage points.

2026-heitmann-russia-s-early-introduction §3 sni-blockinghttp3-quic-blockdpi

QUICstep successfully circumvents the GFW's QUIC SNI censorship (active since April 2024) in live testing. Using an Alibaba VM in mainland China as client and an AWS instance in North Virginia as server, a native QUIC client was blocked after several fetches of youtube.com SNI, while QUICstep consistently succeeded across 50 consecutive fetches. 7 tiktokcdn.com subdomains that were QUIC-SNI blocked were also reliably accessible via QUICstep. The approach routes only QUIC long-header (handshake) packets through a WireGuard tunnel; all subsequent short-header (data) packets travel the native path.

2026-lee-quicstep §4.3.2, §3.2.3 http3-quic-blocksni-blockingdpi

In April 2024 the GFW began decrypting QUIC Initial packets at scale and blocking connections by domain rather than by IP address, targeting the exact transport layer that modern moving-target circumvention systems rely on for session continuity. Because blocking a registrable domain costs the censor essentially zero collateral (unlike blocking a hyperscaler IP range), the censor's optimal Stackelberg budget split allocates f* = 0.97 of its discovery budget to the domain channel once the defender runs n ≥ 2 endpoints (§8.10, Figure 7). GFWatch measurements show hundreds of thousands of domains persistently blocked.

2026-maiti-block-a-mole-sustainability-frontier §1, §3, §6, §8.10, Figure 7 http3-quic-blockdpisni-blocking

Since April 7, 2024, the GFW decrypts every QUIC client Initial packet at China's national border and blocks connections whose TLS ClientHello SNI matches a QUIC-specific blocklist. Blocking takes the form of dropping all subsequent UDP packets sharing the same (src-IP, dst-IP, dst-port) 3-tuple for 180 seconds—with no RST injection. The GFW applies a source-port heuristic: packets with src-port ≤ dst-port are not inspected, capturing >92% of real QUIC client Initials while processing only ~30% of all UDP traffic. The QUIC blocklist contains 58,207 unique FQDNs (Tranco, Oct 2024– Jan 2025), approximately 60% of the DNS blocklist in size; 33% of blocked FQDNs do not actually support QUIC, suggesting the list was derived from an existing domain-name blocklist rather than live QUIC service discovery.

2025-zohaib-quic-sni §3 / §3.1 / §3.3 / §4 http3-quic-blockdpisni-blocking