Art Wildman wrote:
> vivek chal wrote:
>> hello all
>>
>> i have made a server which is acting as a dhcp,dns and internet 
>> gateway in scientific linux 4.5. Now i want my clients won't access 
>> some websites such as orkut,facebook etc . Also i don't want to use 
>> proxy. Please help me .
>>

Use of iptables to control access to websites isn't feasible, because 
it's possible to have many websites at a single IP address, and to have 
one website at many IP addresses.


I don't know a solution that does not use a proxy and a content filter.

> 
> The best practice is to setup filtering with a transparent proxy or 
> bridging firewall, there are other filtering mechanisms which require 
> updating the filters often or manually. There are also custom LiveCDs, 
> Wifi Hotspot Apps & Firewall Distro's that have all this built into a 
> simple appliance distro which may be better suited for your application.
> 
> Setup a transparent proxy with Squid in three easy steps - 200712 NixCraft
> http://www.cyberciti.biz/tips/linux-setup-transparent-proxy-squid-howto.html 
> 
> 
> How To Block WebPages Based On Keywords Or Phrases With SafeSquid Proxy 
> Server
> http://www.howtoforge.com/blocking-webpages-based-on-keywords-or-phrases-with-safesquid-proxy 
> 
> http://www.howtoforge.com/how-to-enforce-google-safesearch-with-safesquid-proxy-server 
> 
> http://www.howtoforge.com/how-to-block-porn-pictures-and-images-with-safesquid-proxy-server 
> 
> 
> How To Set Up Shorewall (Shoreline) 4.0 Firewall On CentOS 5.1
> http://www.howtoforge.com/how-to-set-up-shorewall-firewall-on-centos-5.1
> 
> A parent's guide to Linux Web filtering - 200407 Linux.com
> http://www.linux.com/articles/113733
> 
> DansGuardian
> http://dansguardian.org/

I tried dansguardian some years ago, and found I fairly useless: it 
prevented me from accessing (for example) security documents. It had a 
(long) list of "bad" words, and blocked documents that had too many of them.

I found short documents tended to have relatively few of them and could 
discuss almost anything, whereas log documents, on account of their 
length, tended to have a lot of them and so be blocked.

Of course, ymmv and your experience might be better.

I use squidguard (find it with google): that filters based on URLs, and 
there are free lists.

A problem I have with it is that I don't know how to stop people 
searching for combinations of apparently-innocent words like "office," 
"school," "filter," blocker.

I have found it necessary to block search engines, including google, and 
have a home-build front-end to google.

-- 

Cheers
John

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