A user manual for a third-party ATCA traffic-splitter/bypass appliance ("VELA System" / S3300, made by Beijing Ebright Information Technology Co., Ltd., an ATCA chassis form factor matching the "TSG Ether Fabric" hardware documented elsewhere in this corpus) gives example hardware-level ACL rules that bidirectionally drop any TCP flow on port 80/8080 whose payload contains the literal HTTP header bytes "Content-Type: application/octet-stream", "content-Type: audio", or "content-Type: video" — a raw, DPI-independent, byte-pattern flow-drop capability at the switch/ACL level, distinct from TSG's own sapp/MAAT signature engine.
配置 ipv4 掩码规则 tcp 源端口 80 与关键字 t-Type: application/octet-stream 组合双向流丢弃规则
Defense implications
- Distinctive Content-Type header values on ports 80/8080 can be flow-dropped at the hardware ACL layer before any higher-level DPI classification runs; avoid predictable Content-Type strings for bulk transfer traffic on common web ports.
Related findings
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.
A June 2024 IIE CAS master's thesis (author and advisor names redacted) built a genetic-algorithm + simulated-annealing evasion-traffic generator and, from Sept-Dec 2023, ran live tests against national government HTTP-censorship DPI middleboxes it labels 'RU,' 'KZ,' and 'IN,' plus open-source Snort2/3 and Suricata, cataloging per-target working evasion techniques (e.g. Host-header duplication and field-case manipulation defeat the RU target's Host-based filter; the IN target returns a ~1.2KB block page instead of dropping the connection) in a country-by-technique table, and benchmarked generation efficiency against the open-source 'Geneva' evasion tool from academic circumvention research. NOTE: neither 'ru' (Russia) nor 'in' (India) exists yet as a censor entry in this corpus's taxonomy -- flagged as new-censor candidates; 'kz' already maps to Kazakhstan, a confirmed TSG export site (K18).
The same 2024 IIE CAS thesis proposes 'PED' (Packet-context based Evasion Detection): an XGBoost flow-feature pre-filter followed by a GRU-based autoencoder trained on packet-context features (inter-packet plus protocol-layer, including HTTP-layer fields) that flags DPI-evasion traffic via reconstruction error, reporting accuracy/ROC-AUC above 0.88/0.97 and generalizing to the public CICIDS and MAWI datasets; the thesis also proposes a deployable LAN-gateway evasion-detection prototype and four DPI-middlebox hardening recommendations (mimic Suricata's strict field validation, enforce RFC-compliant parsing, add ML-based anomaly detection, run regular red-team evaluations).
An IIE CAS thesis revision memo shows a student's research was retitled from "measuring evasion attacks against censorship middleboxes" to "evasion-attack traffic generation for DPI middleware" after committee feedback that "censorship middlebox" was too sensitive a term; the work builds evasion-generation tooling (citing Geneva's genetic-algorithm and SymTCP/Alembic's symbolic-execution approaches to TCP state desync) and explicitly tests it against "a specific country's DPI middleware" plus open-source DPI/NIDS, then derives defensive recommendations from the vulnerabilities it discovers.
A complete patent invention-disclosure document describes a "Multipath TCP Functionality Restriction" device deployed inline at a network egress point that identifies the MPTCP TCP option (kind=30, MP_CAPABLE subtype) in initial-handshake SYN/SYN-ACK packets and strips or NOPs it in transit, forcing the connection to fall back to ordinary single-path TCP so that conventional TCP-based inspection and attack detection can be applied to traffic that would otherwise be split across multiple paths.
The internal 'MAAT网络流处理配置统一描述框架' engineering manual (v3.1.20, author name redacted, 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.