Breaking the Great Firewall: The Effectiveness of Government Imposed Internet Censorship – by “John G”

As students at Yale, it is likely you or one of your close friends has spent some time studying abroad in China.  While there, it is likely that they circumvented “The Great Firewall of China,” and if they went while as a Yale undergrad, they likely used Yale’s VPN client service to accomplish this.  For us, the Great Firewall falls with just a single click and a NetID.

Twitter has been blocked in China since 2009

In discussing internet censorship, it is easy to get bogged down in discussions of oppressive government control, Web companies and their compliance/defiance, or the inherent civil rights that may be violated, but the pertinent discussion to have before all of these is: Are these governments actually effective in their attempts to censor the internet?

Reporters without Boarders maintains a list of countries which “censor news and information online but also for their almost systematic repression of Internet users,” and bestows the lovely title of “Enemies of the Internet” to them.  On this list currently are: Burma, China, Cuba, Iran, North Korea, Saudi Arabia, Syria, Turkmenistan, Uzbekistan, and Vietnam.  Each of these countries have a variety of control mechanism in place and are mostly aimed to limit access to information of political opposition, discussion of religion, pornography, gambling, and site about human rights.  To determine the effectiveness of these controls, one must focus on each mechanism, and the ease or difficulty of it’s circumvention. The central tactic is that the government limits the access of the internet to the people,  often being the sole provider. They then are able to monitor the activity of all the users in the country and can limit access through a variety of methods, most of which have a work around to circumvent.

IP Address Blocking

Technique: Blocked IP addresses are made inaccessible. This is one of the most popular techniques, and the main one that is used to block specific sites, such as Youtube in China.  If an IP address is hosted by a web-hosting server, all sites on the server will be blocked.

Circumvention: Establish a connection to a proxy which has access, such as the Yale VPN.  A VPN service has the added bonus of being very secure. Another technique is using a Web to Email service, which emails you the text content of a website of your specification.

Domain Name System Filtering

Tecnique: Blocked domain names, maintained in a registry, will automatically return an incorrect IP or fail to connect.

Circumcision: Input the IP address (try hex and octal if decimal doesn’t work) instead of the domain name, using sites such as NSLookup

Packet Filtering

Technique: Ceases transmission after or takes away access if triggered by uses of keywords.  In Cuba this technique is extended by monitoring word processors, where upon entry of a dissenting keyword the word processor is closed.

Circumvention: Reduce the IP stack’s MTU/MSS to reduce the content of each packet.  If the amount of text is small enough to divide up the trigger words, they will not be detected by the program scanning the string.

Portal Censorship

Technique: Remove specific portals of the internet, such as search engines, making it difficult to find information effectively.

Circumvention: Slowly build up a library of useful domain names and URLs, stumbling from site to site.  This one is really annoying to deal with.

As you can see, the effectiveness of these techniques increases when they are used together.  For instance, blocking search engines and IP addresses would make it difficult to locate an proxy that would circumvent the IP blocker.  However, there is still one tactic that is more powerful than all the rest:

Eliminate Access

Technique: The most extreme case is presented by North Korea, where in efforts to censor information to the public, only specific government officials have internet access.

Circumvention: None


With the exception of the North Korean extreme, there still exists a way to circumvent almost every kind of censorship that these governments impose.  How then can we treat these acts of censorship as effective?  One has to consider the framework of an insider attempting to circumvent from the inside.  We enter this problem with all of our prior tech knowledge and tools.  Most importantly we know of the existence of sites that may be restricted in other countries, and we are able to search ways to circumvent them.  In many of the countries listed above this is not the case, as another one of the main control measures they take is to limit the information about internet circumvention, by the same techniques of IP blocking or packet filtering.  New users in these countries don’t have the groundwork we have from time growing up with unregulated access to information on the internet.

This is the true nature of the control of these countries. It doesn’t matter that they are actually effective in censoring the internet, but that they impede the population.  For us American college kids, full internet access is a necessity. We need our daily doses of Facebook and Youtube or else we will go into withdrawal.  We will find ourselves circumventing these Great Firewalls within a day or two of entering a country that takes removes access from them.  It’s likely that the population of these countries just accept some of their lost access rather than going through the risk and hassle of circumventing it.  The long term goal is to impede the users enough, continually making it more annoying to circumvent so that eventually new users do not even know it is possible, and gaining that information is just as impossible.  At this point the government has become effective in censoring, even though it is not the censoring technology that accomplishes this.

TL;DR: Some governments suck and try to censor the internet with circumventable ineffective means.  The true danger is what happens when people stop bother to circumvent these measures, and give in to the censorship.

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