iptables: drop or reject?

John Summerfield debian at herakles.homelinux.org
Wed Oct 31 01:27:29 UTC 2007


Bill Davidsen wrote:
> 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 that were true, I would expect to see them in my log summary, and I 
don't.




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Cheers
John

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