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Re: Reflexive firewalls?
From: Nick Owen <nickowen () mindspring com>
Date: Thu, 27 Dec 2007 12:10:35 -0500

Ong Chin Kiat wrote:
Hi list,

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?

I call this 'port-knocking' (it might be called reflexive firewalling,
but I have not heard that term).  It can be done with iptables and
googling should turn up a number of how-tos.



Nick Owen
WiKID Systems, Inc.
Commercial/Open Source Two-Factor Authentication
irc.freenode.net: #wikid

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