Re: iptables: drop or reject?

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Ashley M. Kirchner wrote:
 To drop or not to drop, that is the question. If there's a server
out there sending spam e-mail, and I use iptables to block it, is it
best to simply drop the packet, or should I do a '--reject-with
icmp-host-unreachable' (or 'icmp-port-unreachable') or just a 'tcp-reset'?
 Basically, if I just drop the packet, the server in question would
simply continue to send stuff, wouldn't it? As far as it knows, its
spam reached the destination, whereas if I send something back, it might
actually acknowledge and stop? Yes? No?
If you drop, the sending host will often keep sending SYN packets until it decides you are talking, maybe 3-10 packets. If you send back an unreachable status it may not try again until later. I also played with the port-administratively-prohibited status, and a "TOS-host-redirect" packet suggesting the best route to the network was 127.0.0.1. ;-)
I'd reject, in general it will reduce the number of packets you get.

--
Bill Davidsen <[email protected]>
  "We have more to fear from the bungling of the incompetent than from
the machinations of the wicked."  - from Slashdot


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