PushProxy's high-frequency downstream channel generates over 100 push notifications to load a typical webpage, contrasting sharply with the daily average of 46 push notifications received by a smartphone. This statistical anomaly makes PushProxy flows identifiable by simple rule-based filters without requiring sophisticated traffic analysis.

After blocking all *.google.com subdomains on September 22, 2022, China's censor lifted the block specifically for FCM endpoints on October 1 while leaving other Google services (Docs, Groups, Sites) blocked through at least February 2023. This selective whitelist exception — made after only days of blocking — indicates the censor judged the collateral damage to apps relying on FCM to be unacceptable.

§5.1, Figure 5 deployment

Over 7 months of Hyperquack measurements across 5,555,298 probes targeting 1,632 unique ASes, only a small number of ASes actively interfered with HTTPS connections to FCM endpoints. The majority of blocking incidents occurred in China during September 22–30, 2022, coinciding with the Party's National Congress, when nearly all measurements failed with TCP reset.

§5.1, Figure 4 evaluation

PushProxy with N=100 parallel push receivers achieves a median 10 MB download time of 16.46s (~4.86 Mbps) without exceeding FCM's 5,000 messages/hour per-deviceToken rate limit, compared to 2.70s for Shadowsocks and 9.68s for OpenVPN (UDP). This throughput significantly exceeds other service-tunneling systems: dnstt (1.5 Mbps) and CensorSpoofer (64 Kbps).

§5.2, Figure 6 evaluation

PushProxy decouples upstream (XOR-obfuscated UDP) from downstream (FCM push notifications), implementing triangular routing that prevents per-flow traffic analysis: a network adversary with limited visibility cannot correlate upload and download flows since they use different transport protocols and paths. Median TTFB was 572ms versus 492ms (Shadowsocks) and 508ms (OpenVPN), while performance remained stable during Chinese peak hours (20:00–02:00 GMT+8) when Shadowsocks download times increased from 3s to over 100s.

§4, §5.2, Figure 7–8 defense

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

WebSocket, required by HTTPT and WebTunnel to establish covert channels inside TLS connections, had an adoption rate as low as 6.3% of websites in 2021, sharply limiting the pool of volunteer websites that can act as proxies for these tools. By contrast, Huma's traffic replacement scheme embeds covert data in standard HTTP leaf objects (images, scripts, CSS), requiring only that the DW serve HTTP content — a near-universal property.

2026-kamali-huma §II-C dpitraffic-shape

Amnesty International's 102-page investigation identifies a multi-vendor surveillance stack deployed in Pakistan: Chinese DPI (Geedge/MESA-derived), Canadian social-media monitoring (Netsweeper), and Emirati commercial spyware (Pegasus and FinFisher). The system enables deep packet inspection, SNI-based filtering, and traffic-shape classification at national scale, including targeted interception of encrypted messaging apps and VPN traffic.

2025-amnesty-pakistan-shadows §3, §5 dpisni-blockingip-blockingtraffic-shapeml-classifier

VPN search demand in Iran spiked approximately 707% during the June 2025 stealth blackout, as measured by Top10VPN analytics, making it one of the highest-documented circumvention-demand spikes associated with a single shutdown event. Despite this demand, many VPN connections failed because the protocol whitelist eliminated non-HTTPS tunneling methods and HTTP-level filters could detect known VPN signatures on port 443.

2025-aryapour-stealth-blackout §1, §5 dpiport-blockingtraffic-shape