How Iran filters the Internet · Global Voices
Rebecca MacKinnon

Microsoft is not the only U.S. company whose technology is assisting in blocking free speech, and China isn't the only country where it happens.
The OpenNet Initiative and Berkman Center have just released a new report: Internet Filtering in Iran (PDF).   The press release is here (also PDF..sorry).
Here is the executive summary:
Iran has adopted one of the world’s most substantial Internet censorship regimes. Iran, along with China, is among a small group of states with the most sophisticated state-mandated filtering systems in the world. Iran has adopted this extensive filtering regime at a time of extraordinary growth in Internet usage among its citizens and a burst of growth in writing online in the Farsi language. As this report demonstrates, Iran’s sophisticated Internet censorship regime is part of a trend that the OpenNet Initiative’s research has uncovered toward states focusing on blocking expression in local languages, such as Farsi, and with a particular view toward clamping down on what can be published through inexpensive
and popular applications, such as weblogs.
Iran is also one of a growing number of countries, particularly in the Middle East region, that rely upon commercial software developed by for-profit United States companies to carry out the core of its filtering regime. Iran has recently acknowledged, as our testing confirms, that it uses the commercial filtering package SmartFilter – made by the US-based company, Secure Computing – as the primary technical engine of its filtering system. This commercial software product is configured as part of the Iranian filtering system to block both internationally-hosted sites in English and sites in local languages.
SmartFilter, as with all commercial filtering software packages, is prone to over-blocking, errors, and a near-total lack of transparency. In effect, Iran outsources many of the decisions for what its citizens can access on the Internet to a United States company, which in turn profits from its complicity in such a regime.
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Our testing showed that online content in the Farsi language is more likely to be blocked than is comparable content in the English language. We found 499 sites blocked out of 1477 tested (34%) in our November round of tests, and 623 sites of 2025 tested (31%) filtered in our December round. The Iranian state has effectively blocked access of its citizens to many pornographic online sites, most anonymizer tools (which allow users to surf the Internet without detection), a large number of sites with gay and lesbian content, some politically sensitive sites, women’s rights sites, and certain targeted Web logs (“blogs”), among other types of sites.
Iran’s filtering regime is backed up by an extensive series of laws that control the publication of
sensitive information. The press is restrained through a broad set of media-related laws, especially the Press Law of 1986, which includes licensing and substantive regulations. Individuals who subscribe to Internet service providers (ISPs) must promise in writing not to access “non-Islamic” sites. The law requires ISPs to install filtering mechanisms that cover access to both Web sites and e-mail. Punishment for violations of content-related laws can be harsh.
Iran’s filtering regime has certain hallmarks of similar programs across the Middle East region,
such as an emphasis on blocking a large number of pornographic Web sites. Some other aspects of Iran’s blocking – such as that which targets the growing number of Farsi language blogs – sets it apart from other states in the Middle East. Our testing at multiple time periods, including the data in this report and  data previously released in ONI work, show a net increase in the amount of blocking underway in Iran, including additional blocking in some content areas and reductions in blocking in others.