… My heart’s in Accra Ethan Zuckerman’s online home, since 2003

December 23, 2011

SOPA and our 2010 Circumvention Study

Filed under: Berkman,Human Rights — Ethan @ 10:24 am

Daniel Castro of The Information Technology & Innovation Fund recently published a paper supporting the Stop Online Privacy Act (SOPA) currently being debated in congress. In that report, he claims that research performed by us supports the domain name system (DNS) filtering mechanisms mandated by SOPA. This claim is a distortion of our work. We disagree with the use of our study to make the point that DNS-based Internet filtering works and that we should therefore use it as a means of stopping websites from distributing copyrighted content. The data we collected answer a completely different set of questions in a completely different context.

Among other provisions that seek to control the sharing of copyrighted material on the Internet, SOPA, if enacted, would call upon the U.S. government to require that Internet service providers remove from their DNS servers the names of any sites that either infringe copyright directly or merely “facilitate” copyright infringement. So, for example, the government could require that ISPs remove the name “twitter.com” from their DNS servers if twitter.com was not being sufficiently aggressive in preventing its users from tweeting information about places to download copyrighted materials. This practice is known as DNS filtering. DNS filtering is one of the most common modes of Internet-based censorship. As we and our collaborators in the OpenNet Initiative have shown over the past decade, practices of this sort are used extensively in autocratic countries, including China and Iran, to prevent access to a range of sites offensive to the governments of those countries.

Opponents of SOPA have argued that the DNS filtering, even though it will have a number of harmful effects on the technical and political structure of the Internet, will not be effective in preventing users from accessing the blocked sites. Mr. Castro cites our research as evidence that SOPA’s mandate to filter DNS will be effective. He quotes our finding that at most 3% of users in certain countries that substantially filter the Internet use circumvention tools and asserts that “presumably the desire for access to essential political, historical, and cultural information is at least equal to, if not significantly stronger than, the desire to watch a movie without paying for it. Yet only a small fraction of Internet users employ circumvention tools to access blocked information, in part because many users simply lack the skills or desire to find, learn and use these tools.”

In our report, we looked at three sets of censorship circumvention tools: complex, client-based tools like Tor; paid VPNs; and web proxies. We estimated usage of those three classes of tools. We used reports from the client tool developers, a survey to gather usage data from VPN operators and used data from Google Analytics to estimate usage of web proxy tools. Counting all three classes of tools, we estimated as many as 19 million users a month of circumvention tools. Given the large number of users in China, Iran, Saudi Arabia and other states where filtering is endemic, this represents a fairly small percentage of internet users in those countries; 19 million people represents about 3% of the users in countries where internet filtering is pervasive. We actually believe that 3% figure is high, as some of the tools we study are used by users in open societies to evade corporate or university firewalls, not just to evade government censorship.

We stand behind the findings in our study (with reservations that we detail in the paper), but we disagree with the way that Mr. Castro applies our findings to the SOPA debate. His presumption that people will work as hard or harder to access political content than they do to access entertainment content deeply misunderstands how and why most people use the internet. Far more users in open societies use the Internet for entertainment than for political purposes; it is unreasonable to assume different behaviors in closed societies. Our research offers the depressing conclusion that comparatively few users are seeking blocked political information and suggests that the governments most successful in blocking political content ensure that entertainment and social media content is widely available online precisely because users get much more upset about blocking the ability watch movies than they do about blocking specific pieces of political content.

Rather than comparing usage of circumvention tools in closed societies to predict the activities of a given userbase, Mr. Castro would do better to consider the massive userbase of tools like bit torrent clients, which would make for a far cleaner analogy to the problem at hand. Likewise, the long line of very popular peer-to-peer sharing tools that have been incrementally designed to circumvent the technical and political measures used to prevent sharing copyrighted materials are a stronger analogy than our study of users in authoritarian regimes seeking to access political content.

Second, our research has consistently shown that those who really wish to evade Internet filters can do so with relatively little effort. The problem is that these activities can be very dangerous in certain regimes. Even though our research shows that relatively few people in autocratic countries use circumvention tools, this does not mean that circumvention tools are not crucial to the dissident communities in those countries. 19 million people is not large in relation to the population of the Internet, but it is still a lot of people absolutely who have freer access to the Internet through the tools. We personally know many people in autocratic countries for whom these tools provide a crucial (though not perfect) layer of security for their activist work. Those people would be at much greater risk than they already are without access to the tools, but in addition to mandating DNS filtering, SOPA would make many circumvention tools illegal. The single biggest funder of circumvention tools has been and remains the U.S. government, precisely because of the role the tools play in online activism. It would be highly counter-productive for the U.S. government to both fund and outlaw the same set of tools.

Finally, our decade-long study of Internet filtering and circumvention has documented the many problems associated with Internet filtering, not its overall effectiveness. DNS filtering is by necessity either overbroad or underbroad; it either blocks too much or too little. Content on the Internet changes its place and nature rapidly, and DNS filtering is ineffective when it comes to keeping up with it. Worse, especially from a First Amendment perspective, DNS filtering ends up blocking access to enormous amounts of perfectly lawful information. We strongly resist the claim that our research, and that of our collaborators, makes the case in favor of DNS-based Internet filtering.


Mr. Castro’s report may be found here:


with the reference to our work on p. 8.

The study that is being misused by Mr. Castro is here:


The findings of our decade-long studies are documented in three books, published MIT Press and available freely online in their entirety at:


– Rob Faris, John Palfrey, Hal Roberts, Jill York, and Ethan Zuckerman


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  3. The Copyright MAFIAA dismissal of anti-circumvention tools reminds me of Gladwell’s dismissal of network communications tools. The issue isn’t whether networked linkages are as strong as the organizational links within legacy activist movements, but whether networks lower the transaction costs of aggegating weak ties for a common purpose — i.e. whether they make it easier for the strong nodes of the legacy movements to leverage weak ties to those who previously wouldn’t parcipate at all.

    Your example of the importance of activists who use anti-circumvention tools under autocratic regimes, in a larger activist network, was a good one.

    I suspect similarly that for each person who actively uses circumnvention tools in the entertainment world, there’s a larger network of friends who get their music emailed as attachments, or burnt onto CDs and transmitted by sneakerware.

    The heart of stigmergic organization (as KK pointed out re Wikipedia) is the elimination of entry barriers against leveraging small contributions.

    Comment by Kevin Carson — December 28, 2011 @ 12:53 am

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