Using G.711 or G.722-64 codecs (64 Kbps downstream), CensorSpoofer clients in China downloaded Wikipedia's HTML file in approximately 6 seconds and the full 160 KB page in approximately 27 seconds; Tor and a proxy-based system (NetShade) were measurably faster. The iLBC codec limits downstream throughput to 15.6 Kbps, and all codecs impose equivalent dummy-traffic cost on the dummy host (G.711 consumes 87.2 Kbps at the dummy host).

A censor can compare the predicted AS path from the claimed dummy host to the client against the actual observed ingress entry point of the spoofed downstream traffic; inconsistency reveals the dummy host as a cover. For clients in China Telecom (ASN 4134) and China Unicom (ASN 4837), 100% of 225 candidate dummy hosts passed AS-path consistency filtering; for clients in ASN 4538 only 18.2% (41/225) passed, sharply narrowing the usable pool for smaller ASes.

§5.2.3, Table 2 detection

CensorSpoofer decouples the upstream channel (URLs hidden via steganography in IM/Email) from the downstream channel (web content injected into spoofed UDP/VoIP flows), so the proxy's real IP is never revealed to any user. This asymmetric architecture provides perfect insider-attack resistance: even if all users are compromised, they can only learn cover dummy-host IPs, not the spoofer's address.

§4 defense

Port-scanning 10,000 randomly selected non-China IPs found 1,213 (12.1%) acceptable as VoIP dummy hosts (SIP, RTP, RTCP ports not in 'closed' or 'host seems down' states). Of 100 sampled dummy hosts tracked over time, over 90% remained usable for more than 2 hours and over 80% for more than 6 hours; the total usable pool was stable across a 7-day measurement window (Feb. 9–16, 2012).

§7.2.2 evaluation

The MIT ANA Spoofer project shows that over 400 ASes (22%) and 88.7 million IP addresses (15.7%) permit outbound IP address spoofing, constraining where CensorSpoofer proxy nodes can be deployed. ASes applying ingress/egress filtering make IP-spoofing-based downstream channels infeasible from those locations.

§4.2 deployment

A three-stage detection pipeline exploiting the "dual-role" behavioral fingerprint of single-IP circumvention relays achieved 23.2% recall (96/414 ground-truth relays) with a 0.18% false-positive rate against 97,651 benign TLS servers, for an overall accuracy of 99.5%. The ground-truth set covered OpenVPN, WireGuard, and SOCKS relays identified in a 17 TB single-day backbone trace (WIDE Project, April 9, 2025).

2026-almutairi-server §3.4, Table 1 traffic-shapedpiflow-correlation

The paper identifies a fundamental architectural vulnerability in single-IP circumvention designs: a relay must generate new observable flows (via DNS or TLS SNI) to reach end services after receiving client connections, creating a detectable server-and-client behavioral contrast. A relay accessing user-facing domains (news, social media) scores high on a Relay Suspicion Score (w=0.9) versus infrastructure domains (w=0.1). The paper argues this host-level signal is censorship-invariant and cannot be concealed by link obfuscation.

2026-almutairi-server §2.4, §4 traffic-shapedpisni-blocking

Simulations extending the ENEM19 game-theory framework show that ephemeral proxy schemes (modeled on Snowflake/Lantern) effectively neutralize both the "optimal" and "aggressive" censors from the original framework. In overprovisioned settings (proxies arriving at 250/step vs. 200 clients/step), even the null censor scenario outperforms either censor in equal-arrival settings. Over 90% of waiting users receive a proxy within 1 time step. The critical variable is not censor sophistication but proxy arrival rate relative to client demand—high proxy churn combined with high arrival rate defeats both enumeration strategies tested.

2026-fares-game §4, Fig 1, Fig 2, Table 1 dpitraffic-shape

The host-profiling censor (passive traffic analysis: count connections per server, block those exceeding a threshold τ within a window w) blocks essentially all circumvention user traffic within 30 time steps for all classifier qualities tested (ρ_TP ∈ {0.9, 0.95, 0.99}), while causing far less collateral damage than zig-zag (never exceeding ~30% innocent server blocking). Snowflake resists this attack well: with w=3, τ=3, over 94.48% of users receive a proxy within 2 steps even with worst-classifier rules, and final unblocked server rates are 91.24–99.04%. The host profiling approach is feasible for passive censors who cannot enumerate the distribution channel.

2026-fares-game §5.2, Table 2, Table 3 traffic-shapeml-classifier

Multi-censor simulations show that single-censor-optimized distribution strategies perform suboptimally in realistic multi-region deployments. When two networks have different censor strategies (e.g., one optimal, one zig-zag), the distributor cannot detect that a proxy is blocked until all censors have blocked it; this leaves clients without reachable proxies despite the proxy appearing "available" from the distributor's view. The authors conclude that "single-censor evaluation does not accurately predict more realistic deployment performance." A zig-zag censor in one region with 0.25 weight caused 44.4% collateral damage while reducing proxy lifetime to a median of 4 steps.

2026-fares-game §6, Table 4 traffic-shapeflow-correlation

The zig-zag traffic analysis attack (confirmed supported in Geedge TSG leak) rapidly enumerates all static proxy pools. With ζ_watch ∈ {4, 6} steps and a best-quality classifier (ρ_TP=0.99, ρ_FP=0.001), almost total proxy enumeration and user blockage occurs well before step 300. Even ζ_watch=2 leaves ~50% of users blocked. Collateral damage is high across all settings when ζ_watch ≥ 4: eventually ~50% of innocent servers are also blocked. However, Snowflake-style ephemeral proxies resist zig-zag effectively: reachability remains above 95% after 360 steps because churn prevents the censor from expanding its known proxy set beyond agents' direct assignments.

2026-fares-game §5.1, Fig 3, Fig 4 traffic-shapeflow-correlation