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Re: Reflexive firewalls?
From: Ansgar -59cobalt- Wiechers <bugtraq () planetcobalt net>
Date: Thu, 27 Dec 2007 19:44:15 +0100

On 2007-12-28 Ong Chin Kiat wrote:
I've recently used an SSH server that had an interesting
authentication mechanism. You first had to telnet to the machine on a
certain port. After doing this (it will just time out - no prompt),
you then SSH to the server in question. The telnet step has to be
carried out, if not SSH will just time out.

My question is, is this called reflexive firewalling, and can I
duplicate this with iptables?

The technique is called "port-knocking", and yes, it can be done with
iptables. One way to do it is using recent matches.


Ansgar Wiechers
"All vulnerabilities deserve a public fear period prior to patches
becoming available."
--Jason Coombs on Bugtraq

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