The Great Firewall of China is a national effort to protect Chinese corporate and state secrets and infrastructure from cyberattacks. The initiative is overseen by the Chinese Ministry of Public Security (MPS) and officially, the project is known as the Golden Shield.
The firewall is controversial because of fears that the Chinese government is using cybersecurity as justification for controlling what information the country's citizens can access. Sites blocked by the Great Firewall include Facebook, Twitter, the New York Times and Google and its services, including Youtube.
Web sites blocked by the Great Firewall generally appear as though they are experiencing technical issues, rather than providing the end user with any indication that the site has been blocked. Browsers typically return error codes that say a page is not found (404 error), the connection needs to be reset or the page has timed out. The Great Firewall blocks and redirects internet traffic by a number of means, including DNS poisoning, IP address blocks, analyzing and filtering URLs, packet inspection and filtering, resetting connections and blocking VPNs.
As in several other countries, certain keywords are flagged by the government in order to monitor activity. Several sources have confirmed that as of April, 2019, China has blocked Wikipedia across all language URLs. Some Chinese citizens have found ways to circumvent state censorship with proxy servers.