Internet Censorship 101 - DNS Server Filtering

I decided to start a Internet Censorship 101 series of articles that takes a look at and explains the various methods of censorship on the internet and possible solutions to this situation for the user who tries to access information that are blocked / censored. I’m going to start with a relatively weak form of censorship called DNS Filtering.

Whenever you try to access a website you type its url into the address bar. The url is then send to the DNS server who looks up the IP for that website and sends it back to your browser to be able to make the connection to the website. To censor one would simply return no IP or a different IP that redirects to another website. (something like, no no, this is no website that you should visit, bla bla)

This means that the website that you want to access exists of course but the information on the dns server was changed to prevent access. There are two options that let you access the website. The first would be to simply enter the IP address of the website that you want to visit instead of the url. You can use scripts that are freely available on the internet to lookup the IP of an url.

This method is only working if there is only one url that is using that IP. You are out of luck if many websites are hosted on the same server. The second method which is reliable and working for all occasions helps us in this case.

If you change the DNS server that your computer is using to lookup the IP you will receive the correct result. Let us say that you life in China and that China banned access to Wikipedia. Instead of using a Chinese DNS server you use one from the United States which has the information that you need to access Wikipedia.

OpenDNS, a free service, would be one alternative as would be the following list which I have taken from freerk.com

• dns2.de.net - 194.246.96.49 (Frankfurt, Germany)
• ns1.de.eu.orsn.net - 217.146.139.5 (Hildesheim, Germany)
• resolver.netteam.de - 193.155.207.61 (Alfter-Impekoven, Germany)
• sunic.sunet.se - 192.36.125.2 (Stockholm, Sweden)
• master.ns.dns.be - 193.109.126.140 (Leuven, Belgium)
• ns1.lu.eu.orsn.net - 195.206.104.98 (Belvaux, Luxembourg)
• merapi.switch.ch - 130.59.211.10 (Zurich, Switzerland)
• prades.cesca.es - 192.94.163.152 (Barcelona, Spain)
• michael.vatican.va - 212.77.0.2 (Vatican City, Italy)
• dns.inria.fr - 193.51.208.13 (Nice, France)
• ns0.ja.net - 128.86.1.20 (London, UK)
• nic.aix.gr - 195.130.89.210 (Athens, Greece)
• ns.ati.tn - 193.95.66.10 (Tunis, Tunisia)
• ns1.relcom.ru - 193.125.152.3 (Moscow, Russia)
• trantor.umd.edu - 128.8.10.14 (College Park, MD, USA)
• ns1.berkeley.edu - 128.32.136.9 (Berkeley, CA, USA)
• merle.cira.ca - 64.26.149.98 (Ottawa, Canada)
• ns2.dns.br - 200.19.119.99 (Sao Paulo, Brasil)
• ns2.gisc.cl - 200.10.237.14 (Santiago, Chile)
• ns.uvg.edu.gt - 168.234.68.2 (Guatemala, Guatemala)
• ns1.retina.ar - 200.10.202.3 (Buenos Aires, Argentina)
• ns.unam.mx - 132.248.253.1 (Mexico City, Mexico)
• ns.wide.ad.jp - 203.178.136.63 (Osaka, Japan)
• ns.twnic.net - 192.83.166.11 (Taipei, Taiwan)
• ns3.dns.net.nz - 203.97.8.250 (Wellington, New Zealand)
• box2.aunic.net - 203.202.150.20 (Melbourne, Australia)

Changing the DNS Server is a matter of minutes. It depends on the operating system that you are using. In Windows XP you open the control panel and click on network connections. You right-click your connection and select Properties from the context menu.

Select the Internet Protocol (TCP / IP) and click on Properties in that menu. Click on use the following DNS server addresses and enter a preferred and alternate DNS server into the fields. Make sure you enter the IPs. Apply and close the menu and restart your computer. Once that is done you are using the new DNS server which should bypass the censorship.