iptables: drop or reject?
davidsen at tmr.com
Tue Oct 30 21:01:20 UTC 2007
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 <davidsen at tmr.com>
"We have more to fear from the bungling of the incompetent than from
the machinations of the wicked." - from Slashdot
More information about the users