Internet Filtering in China in 2004 2005 

of separating technical difficulties from intentional action, the limited scope of both tests (five proxies, 

one in state run), and the dynamic nature of filtering in China (filtering methods may have changed 

during our testing).   

Figure 2   Testing Method Consistency 

Overall  

In State Match  In State Opposite  Consistency 

Blocked in Proxy Testing 

38 

25 

60% 

Accessible in Proxy Testing 

59 

2 

97% 

TOTALS 

97 

27 

78% 

E. Topics Tested 

Because of the technical challenges of testing in China, including the TCP connection termination 

and  ZeroWindow  condition described below, we performed limited testing in the state.  Our testing 

focused on subjects known to be sensitive to China.  These include political subjects, such as Tibetan 

independence, Taiwanese independence, and the Tiananmen Square incident of June 4, 1989; religious 

subjects, such as the banned Falun Gong / Falun Dafa movement and the Dalai Lama; and broad subjects 

of concern, such as human rights in China, general political opposition, anti Communist material, and 

general news. 

4. R

ESULTS A ND 

A

NA LYSIS

A. Summary 

Our results demonstrate that China's blocking of sensitive content   such as that related to the 

banned Falun Gong spiritual movement, Tibetan independence, or Taiwan   is extensive.  We 

documented instances of overblocking, where sites with superficial similarities to those with sensitive 

material, but different content, were filtered.  This likely indicates China's willingness to tolerate blocking 

unrelated content to prevent access to sensitive materials.  The state's filtering is not perfect   we were 

able to circumvent keyword detection for blog posts, and to obtain some filtered material at alternative 

locations   but it is nonetheless quite thorough.  China's filtering regime is one of the most sophisticated 

in its ability to detect and prevent access to content that the state considers prohibited. 

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