ipfilter traffic blocking and tcpdump snort etc

horio shoichi bugsgrief at bugsgrief.net
Fri Dec 5 02:34:05 PST 2003

On Fri, 5 Dec 2003 00:24:12 +0000
Jez Hancock <jez.hancock at munk.nu> wrote:
> Hi,
> I've blocked a dozen or so addresses using ipfilter:
> block in quick on fxp0 from to any
> block in quick on fxp0 from to any
> etc
> but I still see a lot of traffic those hosts in trafshow, snort and
> other packet capturing utils.  Why is this?
> Is there any alternative method of blocking access from certain hosts
> so that this traffic is not 'seen' by higher level /userland apps?
> As background, the blocked hosts were part of a denial of service attack
> which has been going on for a few hours now.  The attack was aimed at
> port 80, although an odd artifact is that no httpd log entries were made
> for any of the hosts attempting to connect on port 80.
> A cursory nmap scan of a few of the hosts shows that all hosts had both
> port 25 and 80 open, but none of the hosts accepted connections on
> either of those ports.  Any idea what kind of attack this could be?
> -- 
> Jez Hancock
>  - System Administrator / PHP Developer
> http://munk.nu/
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You are probably seeing the supposedly blocked packets on the "outside" of
network. Observe them on "inside", i.e., on the interface not fxp0.

What you are seeing are packets ipfilter is just about to handle.

I don't understand your second question. Are you thinking about tcp wrapper,
reset feature of snort, etc ?

horio shoichi

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