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Date:      Tue, 27 Mar 2001 22:03:36 -0800
From:      Cy Schubert - ITSD Open Systems Group <Cy.Schubert@uumail.gov.bc.ca>
To:        Olivier Nicole <on@cs.ait.ac.th>
Cc:        uknowho@n0mansland.net, freebsd-security@FreeBSD.ORG
Subject:   Re: Filtering inappropriate content 
Message-ID:  <200103280604.f2S648R14405@cwsys.cwsent.com>
In-Reply-To: Your message of "Wed, 28 Mar 2001 11:05:52 %2B0700." <200103280405.LAA16283@banyan.cs.ait.ac.th> 

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In message <200103280405.LAA16283@banyan.cs.ait.ac.th>, Olivier Nicole 
writes:
> >The organization is looking to filter web content only.  Apolgies for
> >the confusion.
> 
> Squid has some rules to do contents filtering I guess.

I tried it.  Squid is not all that effective.  For example, matching 
expressions can be found in perfectly legitimate URL's, e.g. a sun.com 
web page has the character string "sex" in it (I think it was a Virtual 
Adrien component called RICHPsex), so my filter blocked it.  I'm sure 
that operators of web sites that you want to block could name their 
files and directories with non-offending names, bypassing your filter.  
A squid filter may not have the desired effect.

The only solution I can think of that works is to subscribe to a 
service that maintains a database of offending sites.  Cisco routers 
are able to query a system that serves data from databases provided by 
vendors of this service.  Many of these databases block by IP address 
rather than FQDN.  Some even block by network address because operators 
of these sites have been known to move their systems to different IP 
addresses on the same network to circumvent filters based on IP address.


Regards,                         Phone:  (250)387-8437
Cy Schubert                        Fax:  (250)387-5766
Team Leader, Sun/Alpha Team   Internet:  Cy.Schubert@osg.gov.bc.ca
Open Systems Group, ITSD, ISTA
Province of BC




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