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Web filtering through Software


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An Introduction

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Web filtering through Software

  1. 1. Web Filtering
  2. 2. Table of Contents  Need of Filtering  Content Filtering  Basic Model  Filtering Techniques  Email Filtering  Circumvent Filtering  Problems with Filtering  Conclusion
  3. 3. Review About Web Filter
  4. 4. Content Filtering  Analysis of Email and Web content  Prevent malware and spam from entering the network  Determine whether incoming data is harmful to the network or outgoing data includes intellectual property  Such data is then blocked from entering or leaving the network  Simple network layout  Network with traffic proxy Web Security and Anti-Virus
  5. 5. Network Layout Connection is made by forwarding the uninspected traffic straight to the destination. Network with Traffic Proxied Traffic is received by an application which alters the traffic in both the directions before sending to the destination.
  6. 6. Web Filtering Techniques  Firewalls  URL Based Filtering  Content Analysis Firewalls  Basic level of web filtering  Inspects traffic to identify requested site to make decision (allow or block)  Black Lists: Undesirable Web addresses  White Lists: Desirable Web addresses
  7. 7. URL Based Filtering  Database of web addresses  Database loaded onto proxy servers, firewalls and other network infrastructure devices  Supports granular blocking Content Analysis  Keyword Scanning  Image Scanning
  8. 8. Keywords Scanning  Tag words: Positive or Negative score  Block: Sum (score) > Threshold Image Scanning Content Analysis
  9. 9. Email Filtering  Primary communication channel  Need to control SPAM and virus mails Filtering Techniques  Channel/Response: Sender perform task  Heuristic Filters: Score words or phrases  Bayesian Filters: Mathematical Probability
  10. 10. Circumventing Web Filtering Getting around them: Traffic is not passed through the filter.  Getting through them: Traffic is passed through the filter by obscuring the address of content and/or the content itself. Type of Content Tested Accuracy Percentage Content of an Adult Nature – direct URL access 87% Content of an Adult Nature – keyword searches 81% Content not of an Adult Nature – direct URL access 86% Content not of an Adult Nature – keyword searches 69% Image Searches 44% Email Attachments 25% RSS Feeds 48% Catalog Searches 75% Database Searches 88% Internet Filtering Test
  11. 11. Problem with filtering "It could be expected that allowed content would be blocked. If all pornographic content is to be blocked, other content with a resemblance in features will also be blocked; e.g. Adult education, medical information, erotic content etc." “All filters over block. All filters under block. No filter is 100% accurate because no one agrees on what being 100% accurate is.” Conclusion
  12. 12. 1.DansGuardian (Cross Platform, Free) 2.K9 (Windows/Mac, Free) 3.OpenDNS (Cross Platform, Free) 4.SquidGuard/Squid (Linux, Free) 5.Hosts File (Cross Platform, Free) Five Best Content Filtering Tools
  13. 13. Use Of DansGuardian
  14. 14. Reference 1) 2) 3) 4) 5) 6)