Snort mailing list archives
Re: snort is logging alerts but not capturing corresponding packets for some rules
From: Joel Esler <jesler () sourcefire com>
Date: Tue, 26 Apr 2011 19:07:21 -0400
What you should do is output to unified, then use barnyard or something to output to tcpdump format. Joel On Tue, Apr 26, 2011 at 6:25 PM, Kumar, Mahendra <mkumar () intacct com> wrote:
Hi Joel, Can I capture packets in tcpdump mode in snort.log and simultaneously in unified format in some other file? If yes, how can I do that so that I can compare and see if the packets missing from snort.log (tcpdump) are in fact logged in unified format. Thanks *From:* Joel Esler [mailto:jesler () sourcefire com] *Sent:* Tuesday, April 26, 2011 10:49 AM *To:* Agustin Roca *Cc:* snort-users () lists sourceforge net; Jason Brvenik *Subject:* Re: [Snort-users] snort is logging alerts but not capturing corresponding packets for some rules -A cmg on the command line as the alert method. On Tue, Apr 26, 2011 at 1:48 PM, Agustin Roca <agustin.roca () globant com> wrote: Nice explanation Joel. Which snort flag/option can i use to see the *Stream reassembled packet* info? 2011/4/26 Joel Esler <jesler () sourcefire com> Actually, Jason is right. The alert is generated on the pseudo packet, this is correct functionality, so I've closed the bug. So, James, using the pcap you gave me, I'll get rid of the IPs in the cut and paste here, but I'll make BOLD the line that indicates that the alert is actually on the pseudo packet, and not the individual packet. snort -c snort.conf -r missed.pcap -A cmg -q 04/26-10:37:43.307954 [**] [1:12280:3] WEB-CLIENT Microsoft Internet Explorer VML source file memory corruption attempt [**] [Classification: Attempted User Privilege Gain] [Priority: 1] {TCP} x.x.x.x:80 -> x.x.x.x:31390 *Stream reassembled packet* Above, where is says "Stream reassembled packet" is your indication that the alert was not in fact on one packet, but on the reassembly of the packets. We call this the pseudo packet. If you output from Snort in Unified format, you have access to these packets. J On Tue, Apr 26, 2011 at 1:09 PM, Lay, James <james.lay () wincofoods com> wrote: Thanks for the response Jason…I ended up working with Joel on this and he has put in a bug fix. Thanks again. James *From:* Jason Brvenik [mailto:jbrvenik () sourcefire com] *Sent:* Monday, April 25, 2011 5:14 PM *To:* Lay, James; Kumar, Mahendra *Subject:* Re: [Snort-users] snort is logging alerts but not capturing corresponding packets for some rules I would suspect that the event fires on pseudo packets, reassembled or normalized traffic. Can you enable unified2 and see if it is also missing there. On Apr 25, 2011 6:58 PM, "Lay, James" <james.lay () wincofoods com> wrote:From: Kumar, Mahendra [mailto:mkumar () intacct com] Sent: Monday, April 25, 2011 3:50 PM To: snort-users () lists sourceforge net Subject: [Snort-users] snort is logging alerts but not capturing corresponding packets for some rules Hi, I am using snort-2.9.0.5 with daq-0.5-9 and libpcap1-1.1.1-9 on Centos 5.5 (x86_64). I am not using any other thing like unified2, base, barnyard, mysql etc. My snort is working properly and I am getting alerts and packet captures in snort.log in tcpdump format. But for some rules (e.g. SHELLCODE sid:1394) I get the alert logged but there is no packet capture in snort.log and it is very consistent behavior, i.e. I will never get packet captures for some of the rules but will always get alert so it is not a packet drop problem. It seems to be a config issue where the alert is logged but no packet captures. Please help me resolve this issue. Thanks, MK Welcome to my world...I've submitted this exact same item a few times....seems to be a mystery. I have snort boxes in a few different sites on a few different OS's....same thing though...I get the alert in the .fast file, but certain things just do not log to the pcap. I've had to work around this with full web traffic packet captures. The machines aren't even close to maxing CPU or memory, but the problem still persists. If anyone has some advice I'd love to hear it. James------------------------------------------------------------------------------ WhatsUp Gold - Download Free Network Management Software The most intuitive, comprehensive, and cost-effective network management toolset available today. Delivers lowest initial acquisition cost and overall TCO of any competing solution. http://p.sf.net/sfu/whatsupgold-sd _______________________________________________ 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 -- Agustin Roca Information Security Team agustin.roca () globant com work: 54+(011) 4109.1700 ext. 8098 cel: 54+(011)15-5022-3042
------------------------------------------------------------------------------ WhatsUp Gold - Download Free Network Management Software The most intuitive, comprehensive, and cost-effective network management toolset available today. Delivers lowest initial acquisition cost and overall TCO of any competing solution. http://p.sf.net/sfu/whatsupgold-sd
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Current thread:
- Re: snort is logging alerts but not capturing corresponding packets for some rules, (continued)
- Re: snort is logging alerts but not capturing corresponding packets for some rules Joel Esler (Apr 26)
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- Re: snort is logging alerts but not capturing corresponding packets for some rules Joel Esler (Apr 26)
- Re: snort is logging alerts but not capturing corresponding packets for some rules Lay, James (Apr 26)
- Re: snort is logging alerts but not capturing corresponding packets for some rules Joel Esler (Apr 26)
- Re: snort is logging alerts but not capturing corresponding packets for some rules Lay, James (Apr 26)
- Re: snort is logging alerts but not capturing corresponding packets for some rules waldo kitty (Apr 27)
- Re: snort is logging alerts but not capturing corresponding packets for some rules Joel Esler (Apr 27)
- Re: snort is logging alerts but not capturing corresponding packets for some rules Agustin Roca (May 01)
- Re: snort is logging alerts but not capturing corresponding packets for some rules Joel Esler (Apr 26)
- Re: snort is logging alerts but not capturing corresponding packets for some rules Kumar, Mahendra (Apr 26)
- Re: snort is logging alerts but not capturing corresponding packets for some rules Joel Esler (Apr 26)
- Re: snort is logging alerts but not capturing corresponding packets for some rules Jason Brvenik (May 01)