Internet censorship circumvention

Internet censorship circumvention, also referred to as going over the wall () or scientific browsing () 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. Some methods, such as the use of alternate DNS servers, evade blocking by using an alternate address or address lookup system to access the site. Techniques using website mirrors or archive sites rely on other copies of the site being available at different locations. Additionally, there are solutions that rely on gaining access to an Internet connection that is not subject to filtering, often in a different jurisdiction not subject to the same censorship laws, using technologies such as proxying, virtual private networks, or anonymization networks. 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 researchers. Estimates of adoption of circumvention tools vary substantially and are disputed. 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. There are many methods available that may allow the circumvention of Internet filtering, which can widely vary in terms of implementation difficulty, effectiveness, and resistance to detection. Filters may block specific domain names, either using DNS hijacking or URL filtering. Sites are sometimes accessible through alternate names and addresses that may not be blocked. Some websites may offer the same content at multiple pages or domain names. For example, the English Wikipedia is available at Main Page, and there is also a mobile-formatted version at Wikipedia, the free encyclopedia. If DNS resolution is disrupted but the site is not blocked in other ways, it may be possible to access a site directly through its IP address or modifying the .