To censor the Internet painlessly, undetectably, is the dream that keeps repressive governments up late at their mainframe computers. After all, no users are so censored online as those who never see it.The Iranian government is carrying out an Internet crackdown in hopes of subduing the protest movement that has surged since the disputed results of the presidential election on June 12. At the same time, the Iranian government has been sending out the police to restrain protesters and foreign journalists.
http://nytimes.com/2009/06/22/technology/internet/22link.html