IPv6 does not inherently worsen fingerprinting privacy: dual-stack complete sites are measurably harder to fingerprint via IPv6 (45%) than IPv4 (56%), contrary to community fears. The key driver is not the protocol but hosting provider behavior—Cloudflare, Google, and Fastly co-locate large clusters of domains behind a small set of shared IPv6 addresses, creating structured similarity clusters that reduce classifier separability, while Amazon allocates domains across vast unique IPv6 prefixes, increasing fingerprintability.

Encrypted DNS (DoH, DoT) and Encrypted ClientHello (ECH) fully hide plaintext domain names from on-path observers but leave destination IP addresses visible, enabling IP-based fingerprinting with no protocol-level metadata required. An adversary collecting only NetFlow/IPFIX destination-IP records—without TLS fingerprints, packet timing, or port metadata—correctly identifies 72% of all 520K dual-stack websites over IPv4 and 68% over IPv6.

§1, §3, §6.1 evaluation

IP-based fingerprints are operationally stable: approximately 60% of domains exhibit no IP changes across the three-month measurement period for both IPv4 and IPv6. Among churning domains, per-domain churn behavior is comparable across protocols—about 28% of churning IPv4 domains rotate within one hour on average vs 35% for IPv6. Fingerprint databases of ≈100 KB per site (50–60 GB for 520K sites) can be maintained with only periodic DNS re-resolution at negligible overhead for adversaries already collecting NetFlow data.

§6.4, §5.3.2 evaluation

IP-based website fingerprinting achieves 93–94% top-1 accuracy on dual-stack incomplete websites (those with any IPv4-only third-party dependencies) using both IPv4 and IPv6 fingerprints across 228K sites. For dual-stack complete sites (all resources reachable over IPv6), accuracy drops to 56% over IPv4 and 45% over IPv6. The discriminating signal comes almost entirely from secondary resource IPs: using only the primary domain's IP yields 5–8% accuracy regardless of protocol.

§6.1, Table 1 detection

Raw IPv6 address entropy is inflated by continuous discovery of previously-unseen addresses throughout the measurement period (1.04M distinct IPv6 vs 552K IPv4 addresses observed), giving a misleading impression of higher fingerprint discriminability. Realized entropy—computed per crawl-batch snapshot to exclude ephemeral addresses never seen during testing—shows more than 20% of IPv6 addresses provide less information gain than their IPv4 counterparts, explaining why dual-stack complete IPv6 fingerprinting accuracy (45%) underperforms IPv4 (56%) despite higher raw uniqueness.

§6.3, Figure 6, Figure 7 evaluation

The authors propose a 'shim' pluggable transport that splits client traffic across N PT connections using unmodified existing PT bridges as proxies and a gateway bridge that correlates streams back into a Tor circuit via the Turbo Tunnel reliability pattern. This architecture enables all existing and future PTs to benefit from traffic splitting without modifying each PT's client or server code individually.

2024-lorimer-extended §3 website-fingerprintml-classifierip-blocking

Relying on third-party email providers to verify users was demonstrated by Ling et al. to leave Tor's BridgeDB vulnerable to censors capable of creating multiple accounts, enabling bridge enumeration via sock-puppet attacks at scale. Active and passive detection techniques — including traffic flow analysis, DPI, website fingerprinting, and active probing — have been demonstrated in prior work to reveal Tor bridges, making Tor inaccessible for the majority of users in some regions.

2023-tulloch-lox §2.2.1 active-probingdpitraffic-shapewebsite-fingerprintip-blocking

The June 2025 Iran shutdown—carried out during the Iran-Israel war beginning ~June 19—did not use BGP route withdrawals as in 2019. Instead, authorities applied service-level restrictions at the national border: DNS poisoning of foreign destinations, protocol whitelisting permitting only pre-approved domestic services, and DPI to block circumvention-tool traffic. Iran's international traffic fell roughly 90% while the country's BGP routes remained advertised, making the shutdown invisible to BGP-based monitoring systems. OONI measurement volume, which totalled 121,333 in June 2025, collapsed to under 200 submissions on June 19-20.

2025-iran-shutdown-measurement Executive Summary / §2 dpidns-poisoningport-blockingip-blocking

LetsVPN (快连) announced termination of China mainland operations on April 28, 2026, stating the team had attempted adjustments 'almost every hour' for 20 days before concluding the connectivity problem was unsolvable. A follow-up announcement on May 8 declared 'resumption of global standard operations' but explicitly stated it could not guarantee China mainland availability.

2026-anon-2026-27-vpn §3 (快连 / LetsVPN section) ip-blockingdpi

Russia's Roskomnadzor confirmed in February 2026 that it had blocked 469 VPN services used to bypass censorship. Starting December 2025, Russia began blocking the three most commonly used VPN protocols, and from 2025 onward began imposing penalties for promoting VPN services.

2026-anon-2026-27-vpn §5 (Human Rights Watch section) port-blockingdpiip-blocking

In April 2026, Russia nearly completely blocked Telegram, reducing availability without VPN to 5% during the first ten days; Russia's VPN user base was estimated at no less than 40% of the population. Beginning in mid-April, over 20 major Russian websites and platforms (including Gosuslugi, Ozon, Yandex, Sberbank, VK) began restricting access for VPN users, and Russia introduced a whitelist-based service model permitting only state-approved services under certain network restriction states.

2026-anon-2026-27-vpn §4 (俄罗斯 Telegram / OSW section) ip-blockingdpithrottling