Encrypted traffic exhibits a 'full-frequency' spectral property where both low- and high-frequency components are highly active with comparable intensity, unlike natural images which are dominated by low-frequency components. Fourier Transform analysis across CIC-IoT2023, DoHBrw2020, and ISCX-Tor2016 confirms this distinction is pervasive. This signature is an inherent consequence of encryption disrupting byte-level semantics into a visually disordered, noise-like spatial pattern.

FreeUp achieves 86.68% AUC on CIC-IoT2023, 85.44% AUC on DoHBrw2020 (malicious DNS-over-HTTPS tunneling), and 95.53% AUC / 93.22% F1 on ISCX-Tor2016 (Tor anonymous traffic), outperforming all nine baselines by more than 3% AUC on the first two datasets. The ISCX-Tor2016 result demonstrates that frequency-decoupled ML classifiers can detect Tor-like anonymous traffic with high confidence under zero-positive (unsupervised) training.

§V-B, Table I evaluation

FreeUp's dual-branch architecture requires only 0.73G MACs and 6.46M parameters at inference — comparable to or lower than simpler baselines (MFR: 1.01G MACs / 11.18M params; ARCADE: 0.82G MACs / 6.70M params) — while achieving substantially higher detection accuracy. The two branches can be deployed in parallel with minimal memory usage, making frequency-decoupled ML detection computationally practical for real-time network monitoring at scale.

§V-F, Table IV evaluation

Ablation experiments show that removing the high-frequency branch from FreeUp degrades AUC from 86.68% to 77.09% on CIC-IoT2023 (−9.6 pp) and from 95.53% to 95.10% on ISCX-Tor2016. Removing the entire frequency-decoupled framework causes the largest degradation, dropping to 82.10% AUC on CIC-IoT2023 and 81.26% on DoHBrw2020, confirming that high-frequency components are the primary discriminative signal in encrypted traffic anomaly detection.

§V-C, Table II detection

FreeUp operates under a zero-positive (unsupervised) learning paradigm — trained exclusively on normal traffic with no labeled anomaly examples — yet achieves 95.53% AUC on Tor traffic and 85.44% AUC on DNS-over-HTTPS tunneling detection. This demonstrates that frequency-aware anomaly detectors generalize to novel circumvention protocols without requiring any labeled attack data, eliminating the labeling bottleneck that previously limited ML-based censorship detection.

§III, §V-B detection

AEGIS, a flow-physics-only ML classifier using a Hyperbolic Liquid State Space Model evaluated on a 400GB adversarial corpus including VLESS Reality, GhostBear, and AMOI-morphed traffic, achieves F1-score 0.9952, 99.50% TPR, and 0.2141% FPR at 262.27 µs inference latency on an RTX 4090. The system discards all payload bytes and classifies traffic exclusively on 6-dimensional flow physics: packet size, inter-arrival time, directionality, TCP window size, TCP flags, and payload ratio.

2026-ferrel-aegis-adversarial-entropy-guided §V, Table III ml-classifiertraffic-shapefully-encrypted-detect

Internal Geedge documents confirm active contracts to deploy GFW-derived censorship and surveillance infrastructure in Myanmar, Pakistan, Ethiopia, Kazakhstan, and at least one additional unidentified country under the Belt and Road framework, in addition to domestic deployments in Xinjiang, Jiangsu, and Fujian. The exported product (the Tiangou Secure Gateway / TSG line) is not a stripped-down export variant — leaked TSG documentation shows DPI, active-probing, ML classifiers, and granular per-region traffic control rules that mirror the domestic GFW capability set.

2025-geedge-mesa-leak §5, §6 dpiactive-probingml-classifiersni-blockingdns-poisoningfully-encrypted-detecttraffic-shape

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

Censorship classifiers and traffic analysis attacks consistently exploit the initial seconds of a proxy connection, where packet-size, inter-arrival-time, and burst features are maximally discriminative. Cited work demonstrates that website fingerprinting classifiers trained solely on the first few seconds of Tor traffic achieve high accuracy, and real-world GFW detection of fully-encrypted protocols also targets early-connection bytes.

2025-pereira-extended §1 traffic-shapewebsite-fingerprintml-classifierdpifully-encrypted-detect

obfs4 and obfs⋆ produce characteristic wire patterns—bursts of roughly MTU-sized payloads followed by a randomly-sized chaff packet—that CNN classifiers detect purely from packet-size sequences without payload inspection. A trivial per-bridge entropy-biasing re-encoding (obfs⋆) completely defeats the hand-tuned decision tree (0% precision, 0% recall) but does not reduce CNN detectability, because the CNN generalizes across size-distribution variants.

2024-wails-precisely §V-E, §IV-D-3, Figure 4 traffic-shapeml-classifierrandom-payload-detect

Censors optimize for utility under asymmetric misclassification costs rather than raw accuracy: false positives (blocking legitimate traffic) carry economic and political costs that make censors conservative about deploying classifiers with high false-positive rates. Multi-flow stateful classifiers — such as the obfs4 Elligator probabilistic distinguisher, which requires correlating observations across multiple connections — are operationally more expensive than single-packet or connection-initiation classifiers, which the author suggests explains why probabilistic multi-flow distinguishers have not been exploited in practice even when theoretically available.

2023-fifield-comments §5 ml-classifierfully-encrypted-detecttraffic-shape