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The precise number of websites blocked in the United Kingdom is unknown. Blocking techniques vary from one Internet Service Provider (ISP) to another with some sites or specific URLs blocked by some ISPs and not others. Websites and services are blocked using a combination of data feeds from private content-control technology companies, government agencies, NGOs, court orders in conjunction with the service administrators who may or may not have the power to unblock, additionally block, appeal or recategorise blocked content. == Overview == There are a number of different web blocking programmes in the UK. The high profile default ISP filters and IWF filters have been referred to as a "pornwall",〔 "porn filter", "Hadrian's Firewall", "Great Firewall of Britain" and the "Great Firewall of Cameron". However the programmes are usually referred to interchangeable or individually rather than collectively. Inciting racial hatred was removed from the IWF's remit on the setting up of a police website for the purpose in April 2011. The technical measures used to block sites include DNS hijacking, DNS blocking, IP address blocking, and Deep packet inspection, making consistent verification problematic. One known method is ISP scraping DNS of domains subject to blocking orders to produce a list of IPs to block. The Open Rights Group has proposed adding the new HTTP status code '451' to help streamline and add transparency to the process of determining when a site is blocked.〔("451 unavailable - Site blocked for legal reasons" ), Open Rights Group. Retrieved 23 November 2013.〕〔("Open Rights Group revives 'unavailable for legal reasons' HTTP error code plan" ), Simon Sharwood, ''The Register'', 16 August 2013. Retrieved 23 November 2013.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Web blocking in the United Kingdom」の詳細全文を読む スポンサード リンク
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