1. 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 SocietyComputerIssue:310.1109/MC.2010.84IEEE Computer Society Speaker: 侯思帆

2. 摘要 前言 ▫Green Dam Youth Escort Web filter How web filter works ▫IP and URL blackist ▫Content filtering Green Dam

3. 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.

4. 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.

5. IP and URL blackist

7. 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.

8. IP and URL blackist

9. Content filtering Examine various elements of a webpage for classification, including the metadata,link,text,images and scripts

10. Content filtering(Metadata)

11. Content filtering Link ▫For example, a new website is likely linked to other the news sites. Text ▫Semantic and keyword

12. Content filtering Image ▫Skin, but color different

13. 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

14. 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

15. China(black list)

16. Filter Circumvention 請多使用 green dam