Internet censorship circumvention

Internet censorship circumvention, also referred to as going over the wall (Chinese: 翻墙; pinyin: fān qiáng) or scientific browsing (Chinese: 科学上网; pinyin: kēxué shàngwǎng) in China, is the use of various methods and tools to bypass internet censorship.

Various techniques and methods are used to bypass Internet censorship, and have differing ease of use, speed, security, and risks. Censorship circumvention tools, such as Lantern or Psiphon, typically use a combination of many of these approaches. Some methods, such as the use of alternate DNS servers, evade less sophisticated blocking by using an alternate address or address lookup system to access the site. Many censors do not stop at DNS, however, and additionally block the IP addresses of censored domains. Many circumvention tools tunnel network traffic to proxies running in different jurisdictions not subject to the same censorship laws, using technologies such as pluggable transports and traffic obfuscation. Other techniques using website mirrors or archive sites rely on copies of the site being available at different locations.

An arms race has developed between censors and developers of circumvention software, resulting in more sophisticated blocking techniques by censors and the development of harder-to-detect tools by tool developers. Estimates of adoption of circumvention tools vary substantially and are disputed, but are widely understood to be in the tens of millions of monthly active users. Barriers to adoption can include usability issues, difficulty finding reliable and trustworthy information about circumvention, lack of desire to access censored content, and risks from breaking the law.