Are you dropping any packets? It seems that with 3 processes of Snort, on the
same box, with only 2 Gigs of RAM trying to analyze that much traffic, you are
probably dropping packets in addition to Snort overwriting its own memory.
J
On Wed, Nov 22, 2006 at 07:54:34PM +0100, it looks like spagno_f@ifrance.com
sent me:
> Hello,
>
> The machine is a dual Opteron with 2GB of RAM. It runs 3 instances of snort.
> Each snort process sends logs to a specific log directory. Each snort process
> has its barnyard process processing its logs/alerts to the mysql DB. Each
> snort process listens on its own interface. Each interface is attached to the
> SPAN port of a gigabit switch.
>
> Fabien
>
> Joel Esler:
> > How much RAM do you have in your machine?
> >
> > Joel
> >
> >
> > On Tue, Nov 21, 2006 at 06:48:22PM +0100, it looks like
> > spagno_f@ifrance.com sent me:
> > > Hello,
> > >
> > > We encounter a strange problem with snort 2.6.0, Barnyard, BASE, all
> > > compiled from source files.
> > >
> > > We have alerts which do not match the alert rules generating the alert.
> > > Actually, by looking at the payload, we cannot find content we should
> > > see. It seems several people already complained about this problem
> > > before, without any real answer
> > > (http://marc.theaimsgroup.com/?l=snort-users&m=112505975311791&w=2)
> > >
> > > Here is an example below.
> > > We have this rule generating alerts we see in BASE :
> > >
> > > alert ip $EXTERNAL_NET any -> $HOME_NET any (msg:"SHELLCODE x86 NOOP";
> > > content: "|90 90 90 90 90 90 90 90 90 90 90 90 90 90|"; depth: 128;
> > > reference:arachnids,181; classtype:shellcode-detect; sid:648; rev:4;)
> > >
> > > Alert generated by this rule, in BASE :
> > >
> > > #(6 - 56146) [2006-09-29 15:27:22] [arachnids/181] [local/648]
> > > [snort/:648]
> > > SHELLCODE x86 NOOP
> > > IPv4: 172.16.5.27 -> 172.16.5.12
> > > hlen=5 TOS=0 dlen=155 ID=59197 flags=2 offset=0 TTL=128 chksum=45271
> > > TCP: port=3563 -> dport: 1521 flags=***AP*** seq=831827579
> > > ack=2816413717 off=5 res=0 win=16370 urp=0 chksum=12348
> > > Payload: length = 115
> > >
> > > 000 : 00 73 00 00 06 00 00 00 00 00 03 5E 98 20 80 00 .s.........^. ..
> > > 010 : 00 06 00 00 00 00 00 00 00 00 01 0C 00 00 00 00 ................
> > > 020 : 01 00 00 00 00 E8 03 00 00 00 00 00 00 00 00 00 ................
> > > 030 : 00 00 00 00 00 00 01 01 00 00 00 00 00 00 00 00 ................
> > > 040 : 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> > > 050 : 00 00 00 00 00 00 00 00 04 00 00 00 00 00 00 00 ................
> > > 060 : 00 00 00 00 00 00 00 00 00 00 00 00 07 05 C4 05 ................
> > > 070 : 31 0B 07 1..
> > >
> > > As you can see there is no '90' bytes, as we should see in the payload.
> > >
> > > This not the only rule with this problem. Others have the same problem
> > > too (sometimes eevn preprocessors like http_inspect too).
> > >
> > > While looking at the ASCII dump.log file generated by barnyard I have
> > > also came accross a similar exemple (below). For this alert, we should
> > > see a "user" somewhere in the payload, but we don't :
> > >
> > >
> > > [**] [1:2650:2] ORACLE user name buffer overflow attempt [**]
> > > [Classification: Attempted User Privilege Gain] [Priority: 1]
> > > [Xref => http://www.appsecinc.com/Policy/PolicyCheck62.html]
> > > Event ID: 62662 Event Reference: 62662
> > > 11/21/06-17:16:04.892127 172.16.0.136:34833 -> 172.16.5.12:1521
> > > TCP TTL:64 TOS:0x0 ID:32755 IpLen:20 DgmLen:100 DF
> > > ***AP*** Seq: 0xB700F908 Ack: 0xF1594793 Win: 0x3309 TcpLen: 32
> > > TCP Options (3) => NOP NOP TS: 2796076485 835448929
> > > 00 30 00 00 06 00 00 00 00 00 03 68 FB 01 00 00 .0.........h....
> > > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> > > 00 00 00 00 00 00 00 00 00 00 00 04 00 00 00 01 ................
> > >
> > > With this problem Snort becomes almost unusable since, when we try to
> > > analyse an alert to see if this is a false positive or not, we cannot
> > > have the correct payload which generated the alert. We don't know if this
> > > is a Snort or a Barnyard problem. Unfortunately, for now, I was not able
> > > to do a tcpdump of one of these packets.
> > >
> > > Have you noticed the same behavior ?
> > >
> > > What could be the cause of the problem ? What solution to apply ?
> > >
> > > Thank you for your help
> > >
> > >
> > > ________________________________________________________________________
> > > iFRANCE, exprimez-vous !
> > > http://web.ifrance.com
> >
> > > -------------------------------------------------------------------------
> > > Take Surveys. Earn Cash. Influence the Future of IT
> > > Join SourceForge.net's Techsay panel and you'll get the chance to share
> > > your
> > > opinions on IT & business topics through brief surveys - and earn cash
> > > http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV
> >
> > > _______________________________________________
> > > Snort-users mailing list
> > > Snort-users@lists.sourceforge.net
> > > Go to this URL to change user options or unsubscribe:
> > > https://lists.sourceforge.net/lists/listinfo/snort-users
> > > Snort-users list archive:
> > > http://www.geocrawler.com/redir-sf.php3?list=snort-users
> >
> > +---------------------------------------------------------------------+
> > joel esler senior security consultant 1-706-627-2101
> > Sourcefire Security for the /Real/ World -- http://www.sourcefire.com
> > Snort - Open Source Network IPS/IDS -- http://www.snort.org
> > gpg key: http://demo.sourcefire.com/jesler.pgp.key
> > +---------------------------------------------------------------------+
> >
>
>
> ________________________________________________________________________
> iFRANCE, exprimez-vous !
> http://web.ifrance.com
> -------------------------------------------------------------------------
> Take Surveys. Earn Cash. Influence the Future of IT
> Join SourceForge.net's Techsay panel and you'll get the chance to share your
> opinions on IT & business topics through brief surveys - and earn cash
> http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV
> _______________________________________________
> Snort-users mailing list
> Snort-users@lists.sourceforge.net
> Go to this URL to change user options or unsubscribe:
> https://lists.sourceforge.net/lists/listinfo/snort-users
> Snort-users list archive:
> http://www.geocrawler.com/redir-sf.php3?list=snort-users
+---------------------------------------------------------------------+
joel esler senior security consultant 1-706-627-2101
Sourcefire Security for the /Real/ World -- http://www.sourcefire.com
Snort - Open Source Network IPS/IDS -- http://www.snort.org
gpg key: http://demo.sourcefire.com/jesler.pgp.key
+---------------------------------------------------------------------+
-------------------------------------------------------------------------
Take Surveys. Earn Cash. Influence the Future of IT
Join SourceForge.net's Techsay panel and you'll get the chance to share your
opinions on IT & business topics through brief surveys - and earn cash
http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV
_______________________________________________
Snort-users mailing list
Snort-users@lists.sourceforge.net
Go to this URL to change user options or unsubscribe:
https://lists.sourceforge.net/lists/listinfo/snort-users
Snort-users list archive:
http://www.geocrawler.com/redir-sf.php3?list=snort-users
|