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.
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 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.
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.
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).