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.

There are many different techniques to bypass such censorship, each with unique challenges regarding ease of use, speed, and security risks. Examples of tools commonly used include Lantern and Psiphon, which combine a variety of approaches to bypass multiple types of safeguarding. Some methods, such as the use of alternate DNS servers, use false addresses or address lookup systems to evade less sophisticated blocking tools while the user accesses the site. The drawback of this method is that many censors block the IP address of restricted domains in addition to the DNS, rendering the bypass ineffective. Other tools circumvent the tunnel network traffic to proxies from other jurisdictions that do not fall under the same censorship laws. Through the use of technology such as pluggable transports, traffic obscuration, website mirrors, or archive sites, copies of the site available at other locations can be accessed within regions under internet censorship.

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.