SkypeMorph and StegoTorus-Embed fail 5 of 9 standard Skype identification tests (Table I), including the TCP control channel (T9), SoM packet headers (T3), and periodic message exchanges (T6/T7). All failures are detectable by a local (LO) passive censor at line speed without requiring ISP-scale statistical analysis.

Hypothetical fixed parrot systems (SkypeMorph+ and StegoTorus+) that correct all passive detection failures remain unambiguously detectable via active and proactive attacks (Table II). Supernode cache flushing and TCP control channel manipulation — e.g., sending RST causes genuine Skype to drop the call immediately while parrots produce no reaction — distinguish them from genuine Skype because the parrot cannot actually execute Skype protocol logic.

§VII-B, §VII-C, Table II detection

CensorSpoofer's IP-spoofing architecture has an unfixable detection flaw: the spoofer cannot receive or respond to SIP probe messages (INVITE, invalid SIP, BYE for random call IDs) directed at the spoofed dummy host, making four SIP probing tests (Table IV) reliably distinguish CensorSpoofer from genuine Ekiga at local-censor cost. The nmap-based dummy-host selection algorithm identifies only 12.1% of 10,000 random IPs as candidate hosts; SIP probing of 10,000 random addresses found zero IETF-based VoIP clients.

§IX, Table IV detection

The authors enumerate 12 requirements a parrot system must satisfy simultaneously (Correct, SideProtocols, IntraDepend, InterDepend, Err, Network, Content, Patterns, Users, Geo, Soft, OS) while a censor need detect only one failure. They conclude 'unobservability by imitation is a fundamentally flawed approach' and recommend embedding covert traffic in genuine encrypted payloads of a real running protocol (e.g., FreeWave in Skype voice, SWEET in email), which constrains detection to OM adversaries performing large-scale multi-flow analysis.

§XI defense

The StegoTorus-HTTP module returns '200 OK' for non-existent URIs, produces no response to HEAD, OPTIONS, DELETE, and TEST method requests, and omits xref tables from generated PDF files. Using httprecon with 9 request types, the StegoTorus server is distinguishable from any real HTTP server by an OB (resource-limited) censor that records port-80 destination IPs at line speed and fingerprints them offline.

§VIII-B, §VIII-C, Table III detection

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