VPN Gate: A Volunteer-Organized Public VPN Relay System with Blocking Resistance for Bypassing Government Censorship Firewalls

Collaborative spy detection aggregates VPN connection logs (complete, incomplete, and tiny calls) across all volunteer nodes to a central log analyzer, which identifies censor probe IPs by looking for clusters of incomplete or tiny calls from the same /24 block, then distributes a Spy List back to every server so probing packets are silently dropped before the handshake completes. A single server cannot distinguish a spy from a regular client in time; the cross-server aggregate makes pre-response spy identification feasible.

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After VPN Gate blocked the GFW's original probe IP (210.72.128.200, operated by China Science and Technology Network / CSTNET), the GFW authority immediately pivoted to Amazon EC2 and commercial hosting (Gorilla Servers) to enumerate relay lists, using a Python-urllib user agent at fixed polling intervals. Following this adaptation, approximately 80% of all VPN Gate servers became unreachable from China.

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The GFW authority discovered VPN Gate and deployed an automated IP-blocking tool within four days of launch: the List Server was blocked on March 11, 2013 (day 3), and automated scanning of the full server list began by March 12 (day 4). This automated tool polled and blocked all listed IP addresses several times per day.

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Innocent IP mixing — inserting IP addresses of critical Internet infrastructure (DNS roots, Windows Update servers, popular mail servers) into the relay list distributed to users — forces the censor to manually verify each address before blocking. In March 2013, the GFW blocked every IP VPN Gate mixed in within 30 minutes, demonstrating it was trusting the list without verification; after the technique was noticed (March 20), the GFW switched to verifying IPs first, substantially slowing its blocking cadence.

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After deploying innocent IP mixing and collaborative spy detection, VPN Gate raised server reachability from China from a low of ~30% to 78.5% by June 19, 2013, sustaining 60–70% reachability through end of August. On August 29, 2013, VPN Gate served 9,000 daily unique IP addresses from China versus Tor's estimated 3,000.

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