A growing number of states worldwide are imposing mandatory requirements on Internet Service Providers (ISPs) to prevent their subscribers from accessing overseas content that would be banned under local laws. It is well known that undemocratic states such as China implement online censorship; but a number of democracies with constitutional guarantees of freedom of expression are also imposing digital filters. States have further put pressure on Web publishers to remove content hosted outside their jurisdiction (Anderson, 2006).
States’ Internet censorship regimes vary in terms of the types of content blocked and (to a lesser extent) the technologies used. Repressive states block political debat (such as discussion of Tibet or the crushing of the Tiananmen Square protests in China); theocracies impose strict limits on “blasphemous” and “immoral” content, including information on women’s rights and gay and lesbian issues (such as in Saudi Arabia and Iran); while many European states have targeted pornography and racist and xenophobic material (Deibert & Villeneuve, 2005). All of these states have used blocking technologies such as IP address-based packet filtering, DNS poisoning,
cache filtering and keyword searches (Zittrain & Edelman, 2003a).
This article critically examines the Internet filtering regimes and technologies used in a range of democratic and undemocratic states. It considers the effectiveness of
filters, their impact on newer distribution systems such as peer-to-peer networks,
and their compatibility with principles of freedom of expression. It concludes by
contrasting the very limited effect of filters outside totalitarian states on determined users with their potential to impose mass censorship on mainstream Internet users.