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Stephen Clowater wrote: |
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|
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| You can not Block ICMP, it breaks tcp, its a "controll Message Prococol" |
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| for a reason. If you block it, you can not send squelches, routes |
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| unreachable, ect. Point being, block ICMP on your local box, you will |
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| see a few odd problems, but nothing to devestaing. Block it on a pice of |
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| networking hardware, you will $%@#$ up a network. |
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|
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Without attempting to make the thread any longer, the problem with the |
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above logic is that it assumes that the 'firewall' system is not working |
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with 'related' packets. You can drop all the ICMP traffic you want, the |
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required ICMP packets will still get out (and in) so long as the |
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'firewall' system keeps track of 'related sessions'. If an ICMP packet |
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needs to get in and it's related to a current session, the firewall will |
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let it in. If it's unrelated, it's dropped (of course). |
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|
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And that's the whole purpose of ip_conntrack. Any decent 'firewalling' |
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script will implement this. Of course, I've been using Seawall (2.2) and |
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Shorewall (2.4+) for years now without a glitch on personal and |
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corporate/production 'firewalls' and routers. |
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|
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Try: |
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"Keeping track of packets: The state match" |
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http://www.linux-mag.com/2000-01/bestdefense_03.html |
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(part of) |
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"BEST DEFENSE: Network Security With Linux 2.4" |
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http://www.linux-mag.com/2000-01/bestdefense_01.html |
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|
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modprobe ip_conntrack |
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iptables -I INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT |
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|
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Regards, |
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Paul <snafu@××××××××××××.org> |
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|
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BLOG: http://forkbomb.dhs.org/bs/ |
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GPG Key: http://forkbomb.dhs.org/bs/snafu.asc |
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- --- |
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Life would be so much easier if we could just look at the source code. |
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~ -- Dave Olson |
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-- |
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