
Censorship of internet content can take many forms and ranges from governments blocking the dissemination of political opinion to blacklisting pornographic and pirate websites. [...]
According to the ONI data, Iran was the worst ranked, with "pervasive" filtering in the political, social and internet tools categories and "substantial" for conflict/security filtering. Tested in 2011, Iran's filtering was rated as being "highly" consistent and had "medium" transparency. [...]