Re: SNORT or other IDS

From: S. Pidgorny [MVP] (
Date: 11/17/02

From: "S. Pidgorny [MVP]" <>
Date: Sun, 17 Nov 2002 10:58:43 +1100

First of all, see the following KB article and configure servers

Secondly, a device in your Internet connection gateway (e.g. the firewall)
should be able to add some sort of protection against SYN flood - which one
do you use?

Also, SYN flood on internal network can be caused by malfunctioning nework
gear or software package. A protocol analyser and a year of time could help.

Also, take a look at Radware offerings for both DoS protection and BGP -
they have some veru good products...

Svyatoslav Pidgorny, MS MVP, MCSE
-= F1 is the key =-
"" <> wrote in message
> I need HELP   :-)    Below is a post I put somewhere else but no
> response....
> And we have mosts win2k machines being effected which honestly are
> this really really well...    not locking up or denying connections but
> time....
> -----------------------
> I'm in a real tough situation...
> Very large network.    Connection monitoring to numerous webhosts
> shows likely syn flood attack.
> Found out the hard way :-)   All normal protection methods for SYN
> attacks dont work.    Normal Traffic is to large.   Over 100mbps and
> cisco and foundry both crash for tcp intercept functions.
> IDS attached to network.   Can see all in/out traffic.   Snort has no
> ability to detect SynFloods.
> TCPDUMP, can stare at that all day... and have been.    Can not
> associate any single offending host/network.   Well found one that so
> far has over 100k of hits against deny IP acl but blocking had no
> effect on connections to hosts.
> scan all of our hosts...   looking for highest connections in
> TIME_WAIT state...   well....   AOL and other Proxy servers hide any
> indication of half open connecion attacks because the aol proxy ip's
> seem to stay in time_wait for a long time making them the most
> frequent and common connecting hosts
> Our normal traffic is so high that our router w/ 256mb of ram and
> doing default route only with bgp crashes if inspecting 1 class A
> worth of traffic such as
> I can target several Class B's without a problem but I just need some
> blocks to target that would be relevant.
> HELP :-)
> I have Linux IDS plugged in running snort with spade... tcpdump blah
> blah blah...   I can see the full network of traffic...   I just can't
> figure out how to find only half open connections...    AND there is
> also the posibility that we are not being attacked and are having
> bizarre network hardware issues...
> Please Help I'm getting my $%^& kicked by this...
> "Karl Levinson [x y] mvp" <> wrote in message
> news:OXDfM9siCHA.1624@tkmsftngp10...
> >
> > "John C. Olinger" <> wrote in message
> >
> > > I'm looking to trade knowledge with someone who has experience with
> Snort
> > or
> > > another IDS.
> >
> > What do you need to know?
> >
> > There are mailing lists and support groups for Snort and other IDS,
> possibly
> > at and also at
> >
> >

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