For those who don't know what Internet censorship is, it is the control or suppression of publishing or accessing of information on the Internet and in some ways similar to offline censorship.
One difference is that national borders are more permeable online: residents of a country that bans certain information can find it on websites hosted outside the country. Attempts made by one government to prevent its citizens from seeing certain material can have the effect of restricting foreigners, because the government may take action against Internet sites anywhere in the world, if they host objectionable material in the eyes of the restricter.
Barring total control on Internet-connected computers, such as in North Korea, total censorship of information on the Internet is very difficult if not impossible to achieve due to the underlying distributed technology of the Internet.
There are different levels of censorship: Pervasive, Substantial, and Nominal. Below are the countries that fall in the dfferent categories.
While there is no universally agreed upon definition of what constitutes pervasive censorship, organization Reporters without Borders (RSF) maintains an internet enemy list while the OpenNet Initiative categorizes some nations as practicing extreme levels of Internet censorship. Such nations often censor political content and may retaliate against citizens who violate the censorship with measures such as imprisonment.
North Korea : North Korea is not categorized by ONI but is on RSF's internet enemy list. Only a few thousand citizens in North Korea, a tiny minority of the total population, have access to the Internet, which is heavily censored by the national government.
People's Republic of China : The People's Republic of China is in ONI's pervasive category and is on RSF's internet enemy list. China blocks or filters Internet content relating to Tibetan independence, Taiwan independence, police brutality, the Tiananmen Square protests of 1989, freedom of speech, democracy, pornography, some international news sources (such as the BBC), certain religious movements (such as Falun Gong), many blogging websites, and Wikipedia. Some 52 cyber dissidents are reportedly imprisoned in China for their online postings.
Hong Kong and Macau Special Administrative Regions do not censor materials from internet to the same extent. They do block poker sites and other websites they deem inapropriate.
Syria: Syria is in ONI's pervasive category and is on RSF's internet enemy list. Syria has banned websites for political reasons and arrested people accessing them.
Tunisia : Tunisia is in ONI's pervasive category and is on RSF's internet enemy list. Tunisia has blocked thousands of websites (such as pornography, mail, search engine cached pages, online documents conversion and translation services) and peer-to-peer and FTP transfer. This filtering is performed using a transparent proxy and port blocking. Cyber dissidents including pro-democracy lawyer Mohammed Abbou have been jailed by the Tunisian government for their online activities.
Uzbekistan : Uzbekistan is in ONI's pervasive category and is on RSF's internet enemy list. Uzbekistan prevents access to websites regarding banned Islamic movements, independent media, NGOs, and material critical of the government's human rights violations. Some Internet cafes in the capital have posted warnings that users will be fined for viewing pornographic websites or website containing banned political material.
Vietnam : Vietnam is in ONI's pervasive category and is on RSF's internet enemy list. The main networks in Vietnam prevent access to websites critical of the Vietnamese government, expatriate political parties, and international human rights organizations, among others. Online police reportedly monitor Internet cafes and cyber dissidents have been imprisoned for advocating democracy.
South Korea is in ONI's substantial category but is not on RSF's internet enemy list. South Korea has banned at least 31 pro-North Korea websites through the use of IP blocking.
Saudi Arabia: Saudi Arabia is in ONI's substantial category and is on RSF's internet enemy list. Saudi Arabia directs all international Internet traffic through a proxy farm located in King Abdulaziz City for Science & Technology. Content filtering is implemented there, based on software by Secure Computing. Additionally, a number of sites are blocked according to two lists maintained by the Internet Services Unit (ISU): one containing "immoral" (mostly pornographic) sites, the other based on directions from a security committee run by the Ministry of Interior (including sites critical of the Saudi government). An interesting feature of this system is that citizens are encouraged to actively report "immoral" sites for blocking, using a provided Web form. The legal basis for content-filtering is the resolution by Council of Ministers dated 12 February 2001. According to a study carried out in 2004 by the OpenNet Initiative: The most aggressive censorship focused on pornography, drug use, gambling, religious conversion of Muslims, and filtering circumvention tools.
United Arab Emirates : The UAE is in ONI's substantial category and is not on RSF's internet enemy list. The United Arab Emirates forcibly censors the Internet using Secure Computing's solution. The nation's sole ISP Etisalat bans pornography, politically sensitive material, and anything against the moral values of the UAE. Etisalat also blocks VoIP signal and as a result voIP devices do not work from the UAE. Same is tru to aplications such as Skype that rely on the VoIp signal!
Yemen : Yemen is in ONI's substantial category and is not on RSF's internet enemy list. Yemen's two ISPs block access to contents falling under the categories of gambling, adult contents, and sex education as well as material seeking to convert Muslims to other religions.