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Blocking outbound DNS requests.

Posted on 2004-04-09
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Last Modified: 2010-03-18
Good Afternoon Everyone,

I was made aware of a new IRCD bot that has keylogging facilities. Have you guys seen this yet? Kinda scarey.

http://securecomputing.stanford.edu/alerts/multiple-unix-6apr2004.html

In anycase, I was wanting to block all dns requests to a certain domain/ip and was curious to know what would be
the best way to do this without breaking anything. I am running a local DNS server and want to block all outbound
traffic to a certain domain/ip that is requested by my client stations. I would also like to add logging capabilities as
well but am uncertain on how to accomplish this. Just exactly how do I do this in my firewall rule set?

Thanks
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Question by:martinmorales
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jlevie earned 2000 total points
ID: 10794177
Using iptables you'd want to specifically deny FORWARD to that IP/network, something like:

iptables -N firewalled
iptables -A firewalled -j LOG --log-prefix Firewalled:
iptables -A firewalled -j drop

iptables -A FORWARD -p tcp -d 1.2.3.4 -j firewalled
iptables -A FORWARD -p udp -d 1.2.3.4 -j firewalled
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by:martinmorales
ID: 10794986
This worked great! Thank you very much.
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