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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