Re: Reflexive firewalls?

[Nick Owen <nickowen () mindspring com>]

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.

hth,

nick

-- 
Nick Owen
WiKID Systems, Inc.
404.962.8983
http://www.wikidsystems.com
Commercial/Open Source Two-Factor Authentication
irc.freenode.net: #wikid