Re: Range values for TTL

[Max Vision <vision () whitehats com>]

Thanks Fyodor :)

There were a couple of intrusion events that rely on the TTL field..
 IDS3/Traceroute TCP (ttl=1)
 IDS29/probe-Queso Fingerprint attempt (ttl>225)
 IDS115/Traceroute UDP (ttl=1)
 IDS118/Traceroute ICMP (ttl=1)
 IDS439/probe-myscan (ttl>220)

I think that aside from the special case of traceroute, it would be a bad
idea to create rules based on ttl alone (to do passive os detection for
example).. you would have a steady stream of alerts.  passiveOS.pl or some
other post-processing would be better.

Max

On Mon, 7 May 2001, Fyodor wrote:

> On Mon, May 07, 2001 at 01:08:56AM +0800, Tan Chee Leong wrote:
> > Hi,
> >
> > A question about rule-making.  It doesn't seem possible to set a range of
> > TTL values to check.  Did I miss out something?  If it is really not
> > possible, can it be considered in the next version?  This may be very
> > helpful in identifying the platform of the intruder.
> >
> > Pardon me if I have been ignorant in the first place.
>
>
> We had 'ttl: < 5;' and 'ttl: > 6' support before. I just
> added support for : 'ttl: 5-10' (or even 'ttl: - 5;' or
> 'ttl: 5 -;' which is equal to '0-5' and '5-255' range), let
> me know if that's enough for your needs.. :-)
>
> You will need to cvsup current cvs tree. (or wait a day and
> fetch http://snort.sourceforge.net/snort-daily.tar.gz :))
>
> cheers
> -Fyodor
>
>
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