John Palfry:

We at the OpenNet Initiative released our study on Iran today. Of the states that we have studied, Iran has one of the world’s most sophisticated Internet censorship regimes. Iran has demonstrated its commitment to extensive Internet filtering through the targeting of weblogs, particularly those written in Farsi, the local language. The state blocks political, religious, and cultural statements on a range of topics from being written and seen online.

Update: /. has an article up about this