Obscura proxies resist active probing by never exposing open ports or accepting incoming connections; combined with a large ephemeral volunteer pool (analogous to Snowflake's scale), the vast IP address space and rapid proxy rotation make exhaustive enumeration infeasible without causing sufficient collateral damage to deter the censor — consistent with the absence of observed blind-blocking campaigns against Snowflake.

Obscura's browser-to-browser (B-B) WebRTC connections produce DTLS ClientHello and ServerHello messages indistinguishable from genuine browser traffic: across 100 captured handshakes compared against Facebook Messenger, Google Meet, Discord, and a reference WebRTC app using the dfind tool, no unique identifiers were found in C-C connections, and the sole Firefox-specific fingerprint (ServerHello length 86 bytes, cipher TLS_AES_128_GCM_SHA256, extension field length 46 bytes) matches the default Firefox WebRTC profile — meaning blocking it would also block all legitimate Firefox WebRTC users.

§5.2 defense

A differential degradation attack (DDA) that selectively drops RTP packets carrying the last packet of a video frame — exploiting the fact that a single lost packet causes the entire encoded frame to be discarded — reduces Protozoa's covert throughput to single-digit KBps at 1920×1080 with 15% frame loss and at 426×240 with 50% frame loss, while maintaining acceptable video quality for legitimate WebRTC traffic.

§5.3 detection

Under baseline conditions (0% packet loss, no bandwidth constraint, 115 ms RTT), Obscura achieves average throughputs of 1.79 Mbps for Firefox-to-Firefox, 1.49 Mbps for Chrome-to-Chrome, and 1.32 Mbps for Pion-to-Pion connections; P-P connections collapse when the 2 Mbps target video bitrate exceeds the 1500 Kbps bandwidth constraint, while C-C connections remain usable at 10% packet loss with an average of 460 Kbps.

§4.3 evaluation

Authoritarian regimes blocked Snowflake primarily through DPI targeting fingerprints in Pion's DTLS handshake and TLS fingerprints in complementary WebRTC protocols, not through ML-based traffic analysis — confirming that cost-effective censors consistently favor simple, deterministic methods over computationally expensive classifiers.

§1 detection

CensorLess's function refresher automatically retires serverless bridges and deploys fresh ones in batches across diverse regions; the expected time until a bridge is identified and blocked in practice is 2 days (per Fifield et al.), while Tor bridges in China are discovered within 2–36 days. The old bridge is only removed after all clients have completed live migration to a new URL, maintaining uninterrupted connectivity.

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CensorLess's threat model explicitly relies on a rational-censor assumption: the censor will not block entire cloud-provider IP ranges or domain namespaces because the collateral damage to legitimate business services would be politically and economically unacceptable. AWS Lambda's inherent IP-address ephemerality (new IPs on each invocation, function lifetime up to 15 minutes) means even censors willing to attempt enumeration face a continuously shifting target distributed across the cloud provider's global address space.

2026-kang-censorless-serverless §4.2 ip-blockingasn-blackholingactive-probing

InterSecLab's 76-page analysis of the Geedge/MESA leak (based on nine months of indexing and translating >100,000 documents) characterizes the Tiangou Secure Gateway (TSG) product line as a commercially deployable detection stack that combines deep packet inspection, real-time mobile subscriber monitoring, active probing, ML-based traffic classifiers, and granular per-region rule sets. TSG is not a research prototype — leaked documentation includes deployment timelines and client government interactions for Kazakhstan, Ethiopia, Pakistan, Myanmar, and one unnamed country, with censorship rules explicitly tailored to each region.

2025-interseclab-internet-coup §3–§5 (InterSecLab report) dpiactive-probingml-classifiersni-blockingip-blockingtraffic-shapefully-encrypted-detect

Justice for Myanmar documents that Geedge Networks supplied Myanmar's military junta with GFW-derived surveillance and censorship infrastructure under Belt and Road frameworks following the February 2021 coup. The deployed system (Tiangou Secure Gateway / TSG) incorporates the same DPI, active-probing, and ML-classifier capabilities as the domestic Chinese GFW, giving Myanmar one of the most technically capable censorship systems in Southeast Asia.

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Snowflake's sustained operation in heavily censored regions demonstrates that WebRTC must remain accessible to users, which in turn requires that TURN servers remain unblocked to support NAT traversal for peer-to-peer WebRTC connections. This transitive unblockability makes TURN service providers viable rendezvous channels for the Bridge Distribution Problem.

2025-vilalonga-extended §3.2 Bridge Distribution Problem ip-blockingactive-probing

TURN servers used by major applications such as Facebook Messenger for media relay are hypothesized to be less likely blocked in censored regions due to collateral damage to legitimate WebRTC traffic. Providers like Cloudflare, Metered Video, and ExpressTURN supply geographically distributed TURN infrastructure that can be used without any special configuration by a censorship evasion system.

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