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

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 pre-establish 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

•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