I have a couple of questions about Internet censorship in China. I
realize this is a politically sensitive topic, but I'm more interested
in the technical aspects.

- What pages are being censored?
- Who determines whether a page gets censored?
- What technology is being used for censoring?
- When I try to access a censored page in China, how do I notice? Do I
simply get a 404 or, rather, a page that says I'm not allow to view
the page?

Hi! Thanks for the question.

Here are two very good resources that provide detailed information
about how China  accomplishes internet censorship. I think reading the
following articles below is better than providing quotes at this point
since they give a more wholistic explanation to your question.


"Internet censorship in mainland China"
http://en.wikipedia.org/wiki/Internet_censorship_in_China

"Internet Filtering in China in 2004-2005: A Country Study" (Main link
not working at the time I posted this answer. You can go to the Google
cache link instead.)
http://www.opennetinitiative.net/studies/china/ (Link not working at the moment)
http://72.14.203.104/search?q=cache:HWQB4uZPvTgJ:www.opennetinitiative.net/studies/china/+Internet+Filtering+in+China+in+2004-2005:+A+Country+Study&hl=en&ct=clnk&cd=1
 (Google Cache)


The next links are supporting articles and provide additional
information about the China internet censorship issue.

"The Development and the State Control of the Chinese Internet" by
XIAO Qiang, Director, China Internet Project
http://www.uscc.gov/hearings/2005hearings/written_testimonies/05_04_14wrts/qiang_xiao_wrts.htm

"The Great Firewall of China" by Ben Elgin and Bruce Einhorn
http://www.businessweek.com/technology/content/jan2006/tc20060112_434051.htm


Search terms used:  
how internet censorship China works
"Internet Filtering in China in 2004-2005: A Country Study"

I hope these links would help you in your research. Before rating this
answer, please ask for a clarification if you have a question or if
you would need further information.
                                                          
                              
Regards,                              
Easterangel-ga                              
Google Answers Researcher

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Request for Answer Clarification by gabe0505-ga on 26 Jan 2006 01:15 PST

Dear Easterangel,

thanks for your answer!

I scanned the pages you provided links to, but there is one point that
I did not find an answer for:

- When I try to access a censored page in China, how do I notice? Do I
simply get a 404 or, rather, a page that says I'm not allow to view
the page?

The first wikipedia article mentions that DNS poisoning and IP-blocked
blocking are used to block sites. But, if I understand it correctly,
the "fake" DNS entries have to point somewhere. What do users see when
trying to access a blocked page?

gabe0505

---

Clarification of Answer by easterangel-ga on 26 Jan 2006 02:11 PST

Hi again!

It seems that they are not the same in all cases and for all sites.

If you use a search engine here is what you will see according to Wikipedia.

"One part of the block is to disallow certain terms from being used on
search engines. These search engines include both international ones
(e.g. Yahoo! and Google) as well as domestic ones (e.g. Baidu).
Attempting to search for such a term results in a The page cannot be
displayed error.
http://en.wikipedia.org/wiki/Internet_censorship_in_China


Here are some screenshots when someone attempts to make a political
blog at MSN Spaces.

"Screenshots of Censorship"
http://rconversation.blogs.com/rconversation/2005/06/screenshots_of_.html

Another one for Yahoo Results
http://rconversation.blogs.com/rconversation/2005/09/yahoo_chinese_c.html

Examples of when Google was blocked and the URL was redirected in the past.
http://cyber.law.harvard.edu/filtering/china/google-replacements/

In this example, Microsoft cooperated with China and provides an error message.

"Microsoft has capitulated to China by sending an error message to
Internet users in China who use Microsoft's search engine to search
for the Chinese words for democracy, freedom, human rights, or
demonstration, among others. Those who attempt to search for these
words receive an error message announcing "this item contains
forbidden speech."
http://www.theorwellianinternetwatch.com/orwellian_htmls/china_internet.html


I hope these additional information will be of use to you.

Regards,
Easterangel-ga

Thanks for the clarification!

I found this link to be very useful:
http://rconversation.blogs.com/rconversation/2005/06/screenshots_of_.html

It shows that when a page is blocked, the user receives a "Cannot find
server or DNS error". So it seems like the Chinese government does not
point out to users that they are trying to access a blocked page, but
simply lets their HTTP or DNS request fail. Exactly what I was looking
for.

Thanks,

gabe0505

I was in China (Beijing) last Sept. and was getting 404 errors on blocked pages.

Thanks for the kind words, the 5 stars and for the tip! :)

Google.cn will tell you that there has been censorship to comply with
local lawas and that certain results have been removed.

Here is a nice article on C|net about this today:
http://news.com.com/What+Google+censors+in+China/2100-1030_3-6031727.html?tag=nefd.lede