What the Geedge/MESA leak reveals about censor capability

A June 2024 internal MESA Team survey ('针对审查系统的科学研究及探测技术调研报告') catalogs the academic censorship-measurement toolkit (OONI, Augur, Satellite, Quack/Hyperquack, GFWatch, GFWeb, middlebox weaponization studies, traceroute-based middlebox localization, device fingerprinting) and separately reviews circumvention-tool countermeasures, explicitly naming Lantern alongside Psiphon, Tor Meek and Signal as tools using uTLS-style TLS ClientHello mimicry and domain-fronting.

An internal TSG operations/troubleshooting manual lays out TSG's full traffic pipeline (NIC -> mrzcpd/marsio capture driver -> sapp DPI engine -> firewall/proxy(KNI->TFE)/active-defense/WAN-NAT policy branches) and shows engineers using maat_redis_tool to pull the live Redis-synced blocking policy tables (TSG_SECURITY_COMPILE, TSG_OBJ_IP_ADDR, TSG_OBJ_APP_ID) and filter them by numeric policy/object ID to debug why a block rule isn't firing.

The internal 'MAAT网络流处理配置统一描述框架' engineering manual (v3.1.20, author 郑超, 2021) documents MAAT's Redis-synced rule-compilation framework and its RuleScan/Hyperscan-based pattern-matching engine (libmaatframe.so / librulescan), and records that RuleScan's fast-scan feature caused a production outage on 2019-03-19 and has been disabled ever since.

An internal TSG functional-requirements spec ('加密协议JG') defines device support for identifying and blocking ECH, ESNI and QUIC traffic via per-connection SNI/region-matching tables (e.g. DF_QUIC_REGION), plus a companion 'FD报文全流程感知' feature that both passively monitors and actively injects synthetic verification traffic end-to-end through the network path to compute a live per-rule 'CT率' (breakthrough/penetration rate) — the system self-measures how often its own QUIC/ESNI/ECH blocks fail to take effect, and separately throttles logging/blocking detail for rule IDs receiving unusually high hit counts (DF_ATTACK_PROTECTION, 'targeted attack detection').

An internal MESA Lab report (2021-06-25) documents a live test in which a second sapp instance ('sapp B') receives fully decrypted plaintext HTTP traffic via a Unix domain socket from a third-party TLS decryption platform, while sapp A separately captures raw ciphertext via the mrzcpd driver. 24 hours of the decrypted logs (319,569 HTTP records) show the top intercepted destinations are Facebook, Twitter, Google/YouTube and Instagram, with client IPs traced to residential China Telecom/Unicom/Mobile subscribers in Guangdong, Zhejiang and other provinces.

Raw structured DNS event logs (dated 2021-08-23) captured from what appears to be a GFW-adjacent DNS monitoring/injection pipeline use a schema purpose-built for DNS response forgery ('CHEAT_TYPE', 'CHEAT_RCODE', 'CHEAT_STRATEGY', 'CHEAT_RR', 'INJECTED_PKT_FILE' fields) alongside per-query geolocation; sampled records show lookups for facebook.com and tiktokv.com originating from residential China Telecom/Unicom/Mobile subscriber IPs in Guangdong, Zhejiang, Anhui and other provinces, resolving against both domestic and foreign (8.8.8.8, OpenDNS) resolvers.

A MESA Lab monthly report describes a 'web-proxy' engineering task that modified the open-source Ultraviolet web-proxy project to add keyword- and specific-URL-blocking, alongside deployment work (certificate issuance, redirect handling) and a document listing which sites the proxy is permitted to relay; the purpose (internal filtered access vs. a broader capability) is not stated in this excerpt.

A 2023 MESA Lab monthly report describes the 'TF' project's active-defense work: test cases for serial ('串联') HTTP hijack/tamper and parallel ('并联') DNS race-injection ('DNS抢答'), performance tuning that scaled active-defense capacity from 3 to 5 units, converting two existing TSG boxes to active-defense mode, and rewriting the active-defense flow-control logic to no longer depend on sapp.

A MESA Lab monthly report states that adjustments to a VPN-detection module accumulated over 10,000 Psiphon3 server IPs and delayed a Psiphon3 client's ability to get online by at least 3 minutes in the researchers' test environment, an earlier-stage data point consistent with the much larger-scale (~70-73K IP) 'vpn-thwarting'/CyberNarrator Psiphon-harvesting pipeline documented elsewhere in this corpus.

An internal design note for a 'Shadowsocks traffic parsing/restoration module' describes decrypting captured Shadowsocks payloads back to the original HTTP request/response, given a known pre-shared key (AES-256-CFB, MD5-derived key, IV embedded in the stream).

The same internal research note's second research point develops an ML-based detector for Geneva-style automated censorship-evasion traffic; simple flow-level features (flow size, max packet size, RST/SYN/FIN flag counts, forward init-window bytes, inter-arrival timing) achieve near-perfect (ROC-AUC ~1.00) classification of Geneva-generated evasion traffic against CICIDS2017 and MAWI backbone background traffic using decision trees, LightGBM, XGBoost and random forest, with abnormal flow size (~150 bytes vs. 1000-30000 bytes typical) identified as the single most discriminative feature.

An internal MESA Lab research note directly measures and compares China's ('CN') HTTP censorship middlebox against Russia, India and an unlabeled 'HZ' system, plus open-source Snort2/Snort3/Suricata: China is characterized as inspecting Host- and keyword-based triggers (example trigger given: a request containing the parameter 'q=ultrasurf') across ALL ports rather than just 80/443, responding with a triple RST or an extra RST+ACK; an 8-technique HTTP-request-mangling evasion comparison table credits China's middlebox as vulnerable only to request-line whitespace insertion and HTTP-version tampering, fewer categories than the other three systems tested.