Re: router syn/syn-ack/ack alarming...

[Michael Dillon <michael () memra com>]

On Wed, 18 Sep 1996, Vern Paxson wrote:

> > have something in their logs like SYN/ACK RATIO 33:1 POSSIBLE HACKER
> > ATTACK which will make them sit up and take notice.
>
> I don't see how in reality to make the syn/syn-ack/ack ratio work soundly.
> It seems too easy for the cracker to synthesize bogus syn-ack's or ack's to
> manipulate the ratio however they please.

Wouldn't the ratio be calculated from outgoing SYN's and incoming ACK's?
I can see that a sophisticated attacker could have a machine on another
network sending incoming ACK's to balance the outgoing SYN's but I suspect
this would be an extremely small percentage of attacks.


Michael Dillon                   -               ISP & Internet Consulting
Memra Software Inc.              -                  Fax: +1-604-546-3049
http://www.memra.com             -               E-mail: michael () memra com

- - - - - - - - - - - - - - - - -