ICQ Blocking

[Ray Leach]

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Hi

If you need to block ICQ proxied through HTTP, I would suggest blocking the 
entire domain icq.com with some kind of program like squidGuard.

Ray

On Wed 09 Jan 02 11:06, Alexander Demenshin wrote:
> On Wed, Jan 09, 2002 at 03:52:20PM +0800, eddy cheung wrote:
> > Can somebody tell me how to block ICQ with using iptables?  I have block
> > UDP 4000 but it doesn't work.
>
>   ICQ can use different ports as well, and when it couldn't find
> opportunity to connect using standard port (latest versions use tcp 5190 to
> login.icq.com) then it will try other ports/servers, including non-standard
> techniques (like incorrectly formed TCP packets etc). This is "behavior by
> design", attempt of ICQ's developers to avoid restrictions placed by some
> "ugly" admins on corporate networks.
>
>   However, best what can you do - install ICQ on some computer, then record
>   all addresses which it will try to connect to (once you found one, block
> it, then watch for another attempt and so on), then filter out all traffic
> to those hosts/networks (believe me, there is nothing really useful but ICQ
> services itself). But be careful - ICQ can use proxies as well (HTTP
> proxies in particular), so you have to catch this case too.
>
> /Al

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Raymond Leach
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