The Great Firewall of China

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The Great Firewallof China

• By Maysoon Lehmeidi

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How the Firewall Works

• The Great Firewall of China is one of the most
  complex firewalls of its kind. The firewall works
  by preventing IP address from being routed
  through and consists of standard proxy servers at
  the Internet gateways. (1) The firewall also
  uses DNS cache poisoning. DNS poisoning is a
  method that lets the DNS server think it has
  received authentic information, when in reality,
  it has not. (1)
• While most blocked websites are deliberate and
  obvious, most of them are hidden. Many users will
  get what appears to be a network error,
  redirections, or long timeouts rather than a
  blocked web site.
• A request for a filtered web site usually returns
  a network timeout and an HTTP error code. In most
  cases, it was a 404 error, which means that the
  website does not exist even though the website
  was accessible outside of China.

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The OpenNet Initiative

• A study conducted by Jonathan L. Zittrain and
  John G. Palfrey
• They have tested Chinas filtering techniques
  through four different methods
• Manually checking websites to see what was and
  was not blocked by the firewall
• Accessing proxy servers within China
• Creating web logs on three of Chinas most
  popular blog providers to evaluate keyword
  filtering
• Sending e-mails to and from accounts hosted by
  Chinese Internet service providers
• They have classified their results in four
  categories
• URLs accessible both through local connections
  and remote computers (not filtered) (3)
• URLs accessible through local connections but
  inaccessible through the remote computers
  (possibly filtered) (3)
• URLs accessible through local connections but
  inaccessible through remote computers due to a
  network connection error (possibly filtered, but
  not definitive) (3)
• URLs accessible through local connections but
  inaccessible through the remote computer the
  remote computer returns a block page (filtered).
  (3)

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Going Around The Firewall

• Freenet allows users to anonymously circulate or
  retrieve information by pooling the storage space
  of the users. (1) Freenet is currently under
  development. There are drawbacks of using
  Freenet. It is slower and more difficult to use.
• VPN (Virtual private Network) and SSH (Secure
  Shell) connections to outside mainland China are
  not blocked, therefore censorship problems are
  not a big deal to those who have these secure
  connections. Both the Tor website and network
  are not blocked. Tor enables anonymous outgoing
  connections and hidden services. Tor allows
  uncensored downloads and uploads, however, people
  have been caught using Tor because Tor is very
  sensitive to timing. It is not the most reliable
  way to download and upload anonymously.

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elgooG

• As of September 2002, Google became yet another
  name on the long list of banned search engines in
  China.
• However, people can now use Google through a
  mirror website called elgooG.
• elgooG is a website in which all text on the web
  pages as well as the text terms used for searches
  are in reverse and must be viewed through a
  mirror to read what is written. This usually
  involves copying the contents of a site on a
  different server.
• Google has also released information on how
  remotely access its search capabilities. This
  means that other mirror sites can be created
  without having to duplicate Google massive
  database. To date, however, elgooG is the only
  mirror site identified.

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Sources

• Internet censorship in mainland China- Wikipedia
• Chinas Web Watchers- By Matthew Forney,
  Time.com, 10/03/2005
• Internet Filtering in China in 2004-2005 A
  Country Study- By Jonathan L. Zittrain and John
  G. Palfrey, 2004-2005
• The Great Firewall of China- By Charles R. Smith,
  NewsMax.com, 05/17/2002
• Software rams great firewall of China- By Paul
  Festa, News.com, 03/6/2003
• The Great Firewall of China- By Bruce Einhorn,
  BusinessWeek.com, 09/23/2002
• Google mirror beats Great Firewall of China- By
  Will Knight, NewScientist.com 09/06/2002