Table of Contents Need of Filtering Content Filtering Basic Model Filtering Techniques Email Filtering Circumvent Filtering Problems with Filtering Conclusion
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
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.
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
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
Keywords Scanning Tag words: Positive or Negative
score
Block: Sum (score) > Threshold
Image Scanning
Content Analysis
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
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
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
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