Editing Internet censorship in China (section)

===Using Tor and DPI-resistant tools===
Although many users use VPNs to circumvent the Great Firewall of China, many Internet connections are now subject to [[deep packet inspection]], in which data packets are looked at in detail. Many VPNs have been blocked using this method. Blogger Grey One suggests users trying to disguise VPN usage forward their VPN traffic through port 443 because this port is also heavily used by web browsers for HTTPS connections. However, Grey points out this method is futile against advanced inspection.<ref>{{cite web|url=https://greycoder.com/how-hide-vpn-connections/|title=How To Hide Your VPN Connections in China, Iran, United Arab Emirates, Oman and Pakistan – GreyCoder|website=greycoder.com|access-date=2018-04-30|archive-url=https://web.archive.org/web/20180501095349/https://greycoder.com/how-hide-vpn-connections/|archive-date=1 May 2018|url-status=live}}</ref> Obfsproxy<ref name=obsf/> and other pluggable transports do allow users to evade deep-packet inspection.<ref>{{cite web|title=What Is Deep Packet Inspection?|work=pcworld.com|url=http://www.pcworld.com/article/249137/what_is_deep_packet_inspection_.html|date=1 February 2012|access-date=3 January 2015|archive-url=https://web.archive.org/web/20150103091555/http://www.pcworld.com/article/249137/what_is_deep_packet_inspection_.html|archive-date=3 January 2015|url-status=live}}</ref>

The [[Tor (network)|Tor]] anonymity network was and is subject to partial blocking by China's Great Firewall.<ref>{{cite web|title=Torproject.org Blocked by GFW in China: Sooner or Later?|url=https://blog.torproject.org/blog/torprojectorg-blocked-gfw-china-sooner-or-later|access-date=27 May 2012|archive-url=https://web.archive.org/web/20121130131234/https://blog.torproject.org/blog/torprojectorg-blocked-gfw-china-sooner-or-later|archive-date=30 November 2012|url-status=live}}</ref><ref>{{cite web|title=Tor partially blocked in China|url=https://blog.torproject.org/blog/tor-partially-blocked-china|access-date=27 May 2012|archive-url=https://web.archive.org/web/20120512023622/https://blog.torproject.org/blog/tor-partially-blocked-china|archive-date=12 May 2012|url-status=live}}</ref><ref>{{cite web|title=China blocking Tor: Round Two|url=https://blog.torproject.org/blog/china-blocking-tor-round-two|access-date=27 May 2012|archive-url=https://web.archive.org/web/20121128025922/https://blog.torproject.org/blog/china-blocking-tor-round-two|archive-date=28 November 2012|url-status=live}}</ref><ref>{{cite web|title=Picturing Tor censorship in China|url=https://blog.torproject.org/blog/picturing-tor-censorship-china|access-date=27 May 2012|archive-url=https://web.archive.org/web/20120130024220/https://blog.torproject.org/blog/picturing-tor-censorship-china|archive-date=30 January 2012|url-status=live}}</ref> The Tor website is blocked when accessed over [[Hypertext Transfer Protocol|HTTP]] but it is reachable over [[HTTP Secure|HTTPS]] so it is possible for users to download the Tor Browser Bundle.<ref name=HowTorIsBlockingChina>{{cite web|last=Winter|first=Philipp|title=How China Is Blocking Tor|url=http://www.cs.kau.se/philwint/static/gfc/|access-date=27 May 2012|archive-url=https://web.archive.org/web/20120606065132/http://www.cs.kau.se/philwint/static/gfc/|archive-date=6 June 2012|url-status=live}}</ref> The Tor project also maintains a list of website mirrors in case the main Tor website is blocked.<ref>{{cite web|url=https://www.torproject.org/getinvolved/mirrors.html.en|title=Tor Project: Mirrors|website=torproject.org|access-date=2018-04-30|archive-url=https://web.archive.org/web/20171220172642/https://www.torproject.org/getinvolved/mirrors.html.en|archive-date=20 December 2017|url-status=live}}</ref>

The Tor network maintains a public list of approximately 3000 entry relays; almost all of them are blocked.<ref name="HowTorIsBlockingChina" /> In addition to the public relays, Tor maintains bridges which are non-public relays.<ref>{{cite web|title=Tor: Bridges|url=https://www.torproject.org/docs/bridges|access-date=27 May 2012|archive-url=https://web.archive.org/web/20120512012603/https://www.torproject.org/docs/bridges|archive-date=12 May 2012|url-status=live}}</ref> Their purpose is to help censored users reach the Tor network. The Great Firewall scrapes nearly all the bridge IPs distributed through bridges.torproject.org and email. According to Winter's research paper published in April 2012, this blocking technique can be circumvented by using packet fragmentation or the Tor obfsproxy bundle in combination with private obfsproxy bridges.<ref name="obsf">{{cite web|title=obfsproxy|url=https://www.torproject.org/projects/obfsproxy.html.en|access-date=27 May 2012|archive-url=https://web.archive.org/web/20120509232621/https://www.torproject.org/projects/obfsproxy.html.en|archive-date=9 May 2012|url-status=live}}</ref><ref name="HowTorIsBlockingChina" /> Tor Obfs4 bridges still work in China as long as the IPs are discovered through social networks or self-published bridges.<ref>{{cite AV media |date=29 December 2011 |url=https://www.youtube.com/watch?v=DX46Qv_b7F4 |title=28c3: How governments have tried to block Tor |publisher=28c3 |via=[[YouTube]] |access-date=2 December 2022 |archive-url=https://web.archive.org/web/20220715011739/https://www.youtube.com/watch?v=DX46Qv_b7F4 |archive-date=15 July 2022 |url-status=live}}</ref>

Tor now primarily functions in China using Snowflake and meeks which works via front-end proxies hosted on [[Content delivery network|Content Delivery Networks]] (CDNs) to obfuscate the information coming to and from the source and destination, it is a type of pluggable transport. Examples are Microsoft's [[Microsoft Azure|Azure]] and [[Cloudflare]].<ref>{{cite web|url=https://trac.torproject.org/projects/tor/wiki/doc/meek|title=doc/meek – Tor Bug Tracker & Wiki|website=trac.torproject.org|access-date=2019-01-29|archive-url=https://web.archive.org/web/20161213082349/https://trac.torproject.org/projects/tor/wiki/doc/meek|archive-date=13 December 2016|url-status=live}}</ref>