Re: Reflexive firewalls?

[Ansgar -59cobalt- Wiechers <bugtraq () planetcobalt net>]

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.

google://iptables+port-knocking

Regards
Ansgar Wiechers
-- 
"All vulnerabilities deserve a public fear period prior to patches
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