Pakistan is an example of a country that blocks at both the international gateway and at the
ISP level.
There are a few principal techniques used for Internet filtering including IP blocking,
DNS tampering, and proxy-based blocking methods. (For blocking behavior by country, see
table 1.3.) These techniques are presented in further detail by Anderson and Murdoch in
chapter 3.
IP blocking is effective in blocking the intended target and no new equipment needs to be
purchased. It can be implemented in an instant; all the required technology and expertise is
Table 1.3
Blocking techniques
IP blocking
DNS
tampering
Blockpage
Keyword
Azerbaijan
X
X
Bahrain
X
X
China
X
X
Ethiopia
X
India
X
X
Iran
X
X
Jordan
X
Libya
X
Myanmar
X
Oman
X
Pakistan
X
X
Saudi Arabia
X
Singapore
X
South Korea
X
X
X
Sudan
X
Syria
X
Thailand
X
Tunisia
X
United Arab Emirates
X
Uzbekistan*
X
Vietnam
X
X
Yemen
X
X
Blocking behavior included in this table may include international gateway level filtering, and filtering techniques used by different ISPs.
* In Uzbekistan, the blockpage does not clearly indicate that filtering is occurring but rather redirects users
to a third-party Web site.
Measuring Global Internet Filtering
13