All existing automated server-side strategy discovery tools — Geneva, Alembic, and SymTCP — require researcher control of a client during training, even when the discovered strategies are deployed exclusively server-side. This dependency makes it infeasible to train against censors in networks where researchers cannot place a controlled machine.

The proposed crowdsourced system runs multiple isolated Geneva training pools on a controlled server — one pool per censorship system (initially China and Iran) — and instructs volunteer browsers via JavaScript to send forbidden requests to isolated ports, with no download or software installation required from the user. The server monitors per-strategy success or failure to drive genetic evolution entirely from the server side.

§3 Design defense

Browsers cannot independently set the HTTP Host header or TLS SNI field, blocking the standard censorship-trigger methods used in Geneva training. The paper proposes two workarounds: (1) keyword-based HTTP censorship triggers using forbidden strings in URL parameters, limited to censors that employ keyword filtering; and (2) registering domains whose strings contain a censored substring to exploit censor overblocking via overbroad regular expressions (e.g., registering a domain matching torproject.org's regex to also catch mentorproject.org).

§3 Design — Triggering Censorship defense

The system is designed to protect crowdsourced volunteer privacy by storing only AS-level granularity alongside randomized short-lived client identifiers, explicitly discarding source IP addresses and any browser-identifying information. AS-level resolution is sufficient for server-side evasion because strategies are evolved per-censor-ASN rather than per-user.

§3 Design — Protecting Users defense

Server-side censorship evasion strategies require zero client-side changes: clients bypass censorship without installing software or even being aware of the evasion, and this approach has been adopted in production tools including Psiphon's packetman. The packet manipulations exploit weaknesses in how censors track or tear down TCP connections, occurring entirely at the server during the three-way handshake.

§1 Introduction defense

Russian TSPU devices directly block ECH by dropping ClientHello messages that contain both an ECH extension and the outer SNI hostname "cloudflare-ech.com" — the static outer SNI Cloudflare advertises in all its ECH configurations. Blocking affects both TLS and QUIC. ECH connections to servers with Cloudflare ECH support but outside Cloudflare's official IP ranges are NOT blocked. TCP segmentation alone or TLS record fragmentation alone did NOT bypass TSPU ECH blocking, but combining both techniques did circumvent it. TSPU has also added TCP reassembly capabilities that defeat previously effective fragmentation-only bypasses.

2025-niere-encrypted §5, Figure 5 dpirst-injectionmiddlebox-interference

The GFI's HTTP and HTTPS filters are now stateful (requiring initial SYN packet with matching sequence numbers) and have been activated on all TCP ports—not only standard ports 80 and 443 as reported by prior studies. This is a significant departure from previous work that found stateless HTTP/HTTPS blocking limited to standard ports. The HTTP filter injects a 403 Forbidden blockpage (not RST packets as used by the GFW), while HTTPS injects a single RST+ACK packet. The GFI also exhibits TCP non-compliance (not requiring a full three-way handshake to trigger filtering), enabling outside-in measurement without in-country servers.

2025-tai-irblock §2.1, §3.2 dpirst-injectionpacket-injectionmiddlebox-interference

The Henan Firewall is stateless in two exploitable ways: (1) it requires the TCP header to be exactly 20 bytes—enabling any TCP option (e.g., TCP Timestamps, which Windows disables by default) to bypass it entirely; (2) it does not perform TCP reassembly, so splitting a TLS ClientHello across two TCP segments such that the SNI extension straddles the boundary bypasses the censor. Both bypasses require only client-side changes and have already been implemented in Xray, GoodbyeDPI, and Shadowrocket. TLS record fragmentation (splitting the ClientHello across multiple TLS records within one TCP segment) also defeats both the Henan Firewall and the GFW, since neither performs TLS reassembly.

2025-wu-regional-censorship §4.3 / §6 sni-blockingdpimiddlebox-interference

Longitudinal GFWeb data spanning 20 months shows the GFW actively patched previously-published evasion findings during the measurement period: overblocking bugs reported in academic papers were fixed, and fragmented-packet reassembly failures that researchers used to bypass blocking were corrected. This demonstrates that the GFW operator monitors published research and iterates on the system in response to disclosed vulnerabilities.

2024-hoang-gfweb Abstract, §5.4, §6 dpimiddlebox-interference

The SAT Móvil app (Mexico's official tax service, 1M+ downloads) consistently fetches its 'Chat' page over cleartext HTTP, exposing citizen ID numbers (CURP, RFC), passwords, and tax documents to any in-path attacker. None of the four major Latin American telco apps (MiTelcel, MiTigo, MiClaro, MiMovistar) implement HSTS on SMS-delivered external links, making all of them uniformly vulnerable to SSL strip downgrade attacks.

2024-kujath-analyzing §7.2, Table 3 dpimiddlebox-interference

China's Great Firewall showed anomalous inconsistency: 13 test vectors produced mixed outcomes—TCP RST injection on some executions and a clean server response on others—with circumvention rates between 10% and 35% across 100 executions per vector. The authors attribute this to heterogeneous GFW infrastructure components applying different HTTP parsing logic, a departure from the GFW's usual consistency.

2024-m-ller-turning §5.2 dpirst-injectionkeyword-filteringmiddlebox-interference