Web Filtering and Censoring
This paper appears in: Computer
Issue Date : March 2010
Volume : 43 , Issue:3
On page(s): 94
ISSN : 0018-9162
INSPEC Accession Number: 11171565
Digital Object Identifier : 10.1109/MC.2010.84
Date of Current Version : 11 三月 2010
Sponsored by : IEEE Computer Society
Speaker:侯思帆
摘要
• 前言
▫ Green Dam Youth Escort Web filter
• How web filter works
▫ IP and URL blackist
▫ Content filtering
• Green Dam(綠壩)
IP and URL blackist
• 缺點:
▫ First.continual blackist updating requires
enormous effort and resources.
▫ Second IP blacklist work at a coarse
granularity-the filter either blocks or
allows all web content from an IP address.
IP and URL blackist
• Implemented at DNS servers that resolve
domain names to ip address. When a DNS server
receives a recolution request, it check the URL
is on the list, the DNS server will return an
incorrect or default IP address.
IP and URL blackist
IP and URL blackist
Content filtering
• Advantages Over IP or URL blacklist
• First ,ther filter examines web contents when a
page is requested ,without the need to preestablish a blacklist.
• Second the filtering decision is based on
individual web-pages or even elements within a
page.
IP and URL blackist
Content filtering
• Examine various elements of a webpage for
classification , including the metadata ,link ,text
,images and scripts
Content filtering(Metadata)
Content filtering
• Link
▫ For example, a new website is likely linked to
other the news sites.
• Text
▫ Semantic and keyword
Content filtering
• Image
▫ Skin , but color different
Green Dam(綠壩)
• First
▫ check URL blacklist
• Second
▫ cans text obscenities and politically sensitive
phrases
• Third
▫ Image scanner (skin color)
▫ Svm(support vector machine) ,以其它過濾條件補
強
Green Dam(filtering content)
• Political dissent(持不同政治意見)
• Social deviance for example
pornography,gambling
• National security threats- terrorism
• Certain internet services – blogs,peer to peer
China(black list)
Filter Circumvention
• 請多使用 green dam