A confidentiality-marked ("内部资料 注意保密", 架构组/Architecture Group) MESA Lab research report systematically profiles 11 video-conferencing/collaboration platforms (DingTalk, Zoom, Feishu/Lark, WeCom, Tencent Meeting, WebEx, Huawei WeLink, Slack, Teambition, 科技云会, 小鱼易连) with SNI lists, TLS certificate fingerprints, DNS/whois infrastructure, and an explicit "passive traffic analysis feasibility" (被动流量分析可行性) verdict per app — direct precursor engineering work for per-app DPI detection signatures.
虽然有飞书设计多个字节跳动，头条相关的特征，但feishu是一个独特的特征，可以基于此进行被动流量分析 ... SNI特征 Server Name: lvcio.bytedance.com ... Server Name: passport.feishu.cn ... Server Name: open-hl.feishu.cn
Defense implications
- Any distinctive SNI substring is treated as sufficient for a per-app signature even when the app shares TLS/cert infrastructure with a much larger platform (Feishu inside ByteDance's cert/CDN estate) — a pluggable transport that fronts through shared big-tech infrastructure must not leak any protocol-specific SNI substring of its own.
Related findings
A dedicated internal "运营商前端分析团队" (Carrier Front-end Analysis Team) produces weekly, carrier-specific traffic-analysis reports explicitly titled "新疆移动流量分析报告" (Xinjiang Mobile Traffic Analysis Report) and "新疆联通流量分析报告" (Xinjiang Unicom Traffic Analysis Report), with instances dated from at least July 2022 through March 2024. One instance (Xinjiang Mobile, 2023-05-15) reports total carrier bandwidth of 4.4Tbps (1Tbps access bandwidth), 27.34PB of weekly throughput, 123 distinct identified application-layer protocols, and a section (4.1, pages 17+) explicitly tracking server IP/location for 28 named overseas apps (BBC, Discord, ESPN, Facebook, Gmail, Google, Hulu, Instagram, Netflix, Reddit, Skype, Telegram, Twitter, Uber, WhatsApp, Wikipedia, YouTube, Zoom, etc.).
The Transformer_master.h header (part of the Maat/sapp DPI framework, dated 2023-05-04) defines a region-keyed DNS response-forgery subsystem (MSG_OPT_DNS_CHEAT_TYPE/RCODE/STRATEGY/RECORD/TTL, DNS_FAKE_INFO/DNS_FAKE_IP tables, TF_get_dns_response_strategy_id(user_region)) used specifically by the block ("FD") action path, plus a dedicated function to classify whether a detected L7 protocol is a VPN (TF_is_L7_vpn_prot), and native extraction of TLS JA3/JA3S client and server fingerprints.
A raw production SSL/TLS session log from sapp's monitoring pipeline (timestamps dated 2021-08-23, client IPs in domestic Chinese carrier ranges) shows the per-connection logging schema includes dedicated fields for a captured certificate chain (INDIVIDUAL_CERT_FILE, MIDDLE_CERT_FILE, ROOT_CERT_FILE, CHAIN_CERT_FILE) and for any injected packet (INJECTED_PKT_FILE), alongside SNI and TLS version -- confirming sapp's live SNI-logging and MITM-cert-capture instrumentation was operating against real user traffic to services including huobi.com, steamcommunity.com, and dropbox.com.
MESA_Platform's "quic" module (built and packaged as stellar-on-sapp/sapp RPMs) implements SNI/User-Agent extraction from both cleartext GQUIC (versions 23-59) and encrypted IETF QUIC RFC9000 ClientHello payloads, and supports a QUIC SNI whitelist -- i.e. the DPI pipeline decrypts/parses encrypted QUIC handshakes to recover the destination domain rather than being blocked by QUIC's encryption.
TSG's application-fingerprinting engine matches 'FlyVPN' via a combination of IP-address and FQDN/port feature objects (each independently versioned/timestamped); a false-positive bug investigation confirms the live traffic-classification component is called 'sapp' and that restarting it is a standard troubleshooting step for signature drift.
The Fujian (domestic China) deployment uses a punycode/IDN-aware keyword-filtering policy object named '中文涉诈域名' (Chinese fraud-related domains) with wildcard item matching; a bug ticket shows the policy engine failing to match an IDN punycode domain correctly against this object, revealing the underlying components: a 'verify-policy' microservice, and libraries 'libmaatframe' and 'librulescan' handling rule evaluation.