Internet Filtering in China in 2004 2005 

5. Tibet 

We tested several URLs containing the strings  tibet  or  dalai .  All were blocked in proxy 

testing; only a Swiss travel guide was blocked during in state testing. 

Figure 26   Tibet Overblocking 

In State 

Proxy 

Sites Tested 

Result 

Result 

Description 

http://www.tibet.cn/ 

Accessible 

Blocked 

China Tibet information center 

http://www.dalai.com/ 

Accessible 

Blocked 

Dalai software, Mexico 

http://www.pmgeiser.ch/tibet/ 

Blocked 

Blocked 

Tibet travel guide 

Total (3 sites) 

33% 

100%   

E. Mechanics of China's Filtering 

Our results elucidate several interesting characteristics of how the underlying filtering 

infrastructure in China operates. 

1. Underinclusive IP Address Blocking 

For a subset of the sites we tested, we also attempted to reach the site at its IP address.  To 

prevent access to a site completely, a filtering regime cannot block only its URL, but must also filter its IP 

address.  We tested both the URL and the IP address during in state testing for 29 sites; in 24 cases, the 

result was consistent (both were either blocked or accessible).  Four sites (www.fofg.org, 

www.freetibet.org, www.tibet.com, and www.lnx bbc.org) could not be reached at their URLs, but were 

accessible at their IP addresses.  We believe that the blocking of www.lnx bbc.org is inadvertent, and thus 

it is not surprising that its IP address is accessible.  However, the other three sites clearly contain sensitive 

content, but are not filtered at their IP addresses.  Thus, while China blocks both IP addresses and URLs 

to ensure that sensitive sites are filtered, it does not do so consistently. 

2. URL vs. Domain Level Filtering 

Our research indicates that filtering states generally block on a domain by domain basis; they 

prevent access to an entire domain rather than filtering individual Web pages and URLs.  The exceptions 

to this behavior tend to be domains containing large amounts of diverse, unrelated content, such as the 

free Web hosting domain geocities.com or Yahoo!'s groups.

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  Our in state testing in China, however, 

found several instances where particular URLs were blocked but the domain was accessible, though the 

source (authorship) of content appeared consistent across the domain.  For example, the URL 

www.stanford.edu/group/falun was blocked, but www.stanford.edu was not.  The following sites were 

blocked while their top level URLs were accessible: 

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 In addition, commercial filtering software such as Secure Computing's SmartFilter often assigns different pages 

within a domain to different categories; thus, some pages, but not the entire domain, are filtered when a filtering state 

selects categories to block. 

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