An internal MITM-attack training/research presentation demonstrates a live keyword-filtering test through a trusted-root-CA MITM proxy (mitmproxy) against HTTPS traffic to scholar.google.com: after installing the MITM root certificate on the client, searches containing a prohibited keyword (drugs, 毒品) fail to load while normal searches succeed, in both forward-proxy (via an Aliyun VPS relaying through the circumvention tool Clash) and transparent-proxy configurations. The same deck describes a separate built tool, "video_server," that MITM-intercepts and downloads WeChat Channels (微信视频号) video content, and covers SSH/RDP MITM techniques (including the SSH Terrapin attack) more broadly.
在用户PC终端安装Mitmproxy根证书，使用Chrome浏览器访问https://scholar.google.com，可以进行https访问，说明使用信任根证书进行中间人代理。在其页面搜索毒品等违禁词，会出现无法访问页面，而搜索正常内容，可以正常访问
Defense implications
- This is a demonstrated (not just theoretical) capability chain: trusted-root MITM implant -> decrypted HTTPS -> keyword match on request content -> selective block, tested against a real global service (Google Scholar). Treat TLS interception + content-layer filtering as a validated combination, not a hypothetical one, when threat-modeling any deployment where a client-side root CA could plausibly be installed.
Related findings
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 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.
An internal 'MAAT Configuration Description Manual (String)' fully documents MAAT's rule-compilation model: per-field string matches (substring/prefix/suffix/exact/regex/AND-of-substrings/offset-anchored substrings) grouped into up to 8 AND/NOT clauses per compiled rule (conjunctive normal form), each carrying an action code (0=block, 1=monitor-only, 2=whitelist), blacklist and logging flags, and a floating-point execution-order field for safe rule reordering, plus the C scanning API (Maat_full_scan_string) and the file/JSON formats used to push rule updates to production.
Internal MAAT engineering Q&A notes detail the rule engine's filter hierarchy: a 'region' config matches on keyword / regex / IP / extended-IP(CIDR) / numeric / file-digest / text-similarity / FQDN fields; regions roll up via AND/OR into 'group' configs; groups roll up into an 8-clause-max 'compile' config in conjunctive normal form. Rule config is pushed via a Redis single-primary/multi-replica tree, and MAAT itself is not distributed — each production front-end box runs its own single MAAT instance that receives pushed config and calls the shared rulescan library to execute the actual scan.
A weekly operational report documents newly-added blocking rules for 25 mobile apps (18 hosted overseas, mostly on Hong Kong-region Azure/Alibaba/Tencent cloud IPs), where analysts extract each app's domains, IPs, and distinctive URL paths (e.g. '/tigase/getLastChatList', '/user/getUserMoney') and log 'system disposition: newly added blocking action' for every one; matching raw keyword-object exports using the identical URL-path style confirm these hand-extracted paths are loaded directly as live filter-list entries in production.
The AppSketch/MAAT signature system contains a systematically dated, patch-versioned catalog of FQDN-based detection signatures for dozens of individually named commercial VPN apps (e.g. V2VPN, V2Netvpn, Turbo VPN, LetsVPN, AdGuard VPN, Avira Phantom VPN, TouchVPN, FinchVPN, Opera VPN, Ultrasurf VPN, GoFly VPN), each modeled as an 'app' object in category 'networking' / subcategory 'tunnels' whose default deny_action drops the flow while sending both an ICMP-unreachable and a TCP RST to the client. At least 35 such distinct VPN-app signature objects appear in this batch alone, dated July-November 2024, with repeated 'Patch0N' revisions to the same app as its domains rotate.