Re: an anternative to port-knoking using the OpenBSD pf only

On Mon, 23 Jan 2006 22:44:52 +0100
poplix <poplix@papuasia.org> wrote:
>    OUT (tcp.flags='syn')
>     set(
>      tcp.win='8192',ip.ttl='128',ip.flags.df='0',
>      tcp.options='mss=3884+noop+wss=0+noop+noop+ts=TS'
>     );
>
>    This rule tells tripp to rewrite all outgoing tcp packets with
> the SYN
>    flag set only allowing my first handshake packet to match "poplix"
>    fingerprint.

Does an attacker who wants to attack a server include aspect that
this maybe a system utilizing port knocking in this way?
Perhaps if he has focused at this system?

Am i right to say, your invented os fingerprint is random and unique 
and because of unlimited IP option field's length there's no
chance left for attacker to brute force ports with different option
field values et cetera to get correct option field + window size + ttl +
flag?

regards

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