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Blocking IM (MSN, Yahoo Messenger) using Squid

Posted on 2004-09-01
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Last Modified: 2013-11-22
I have Squid running and I am looking for a way to block Yahoo and MSN messenger. My search of the Internet has not come up with any working solutions.

Has anybody been able to successfully block these IM programs using Squid?

Setup:

Squid 2.4 Stable6
OS: FreeBSD 4.9

Thanks in advance
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Question by:cchinoy
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by:gheist
ID: 11975468
1) Install all messengers you can imagine - Yahoo! , MSN , AIM , ICQ and Trillian
2) Install packet sniffer like ethereal on workstation
3) now try running all messengers one at a time
4) now look for common signs on how to block them

For example AIM uses host login.oscar.aol.com
MSN Messenger uses MIME type containing "X-MSN-Messenger" string

Same applies to digital media players, spywares, viruses etc.

Never try to use these programs when they are blocked for common users.
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by:cchinoy
ID: 12102723
Thank you I will give this a try
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jdw_2004 earned 500 total points
ID: 12132638
These applications use ports other than HTTP.  In fact, these programs are particularly tenacious in their efforts to circumvent restrictions.  Also, for what web accesses they do perform, instant messaging clients may or may not honor the system's proxy configuration.  

Thus, you will not be able to effectively block IM programs using squid, without assistance from a firewall or router.  Even then, eternal vigilance will be required as these programs find new ways to weasel through with each new release.

The following page is very helpful:

http://nscsysop.hypermart.net/no_chat.html

This previous EE question may also be instructive on firewall blocking, if you want to go that route:

http://www.experts-exchange.com/Security/Firewalls/Q_20610865.html

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