Snort mailing list archives

Re: getting a full copy of pcap for forensic purpose from Snort


From: Jeremy Hoel <jthoel () gmail com>
Date: Thu, 20 Mar 2014 16:44:49 +0000

We use daemonlogger, snort and cxtracker all listening to the same NIC;
it's not that busy in most cases 100-300MB on the worst box, but we have no
issues.  We use OpenFPC as the controlling agent for daemonlogger and
cxtracker it we can pull pcaps from all our sensors with just one script.
 It works great.

All of this is on CentOS 6.x boxes too.. so nothing exotic or crazy.


On Thu, Mar 20, 2014 at 1:48 PM, Long, Kerry S <kslong () mitre org> wrote:

 I looked at daemonlogger before.  I looked kind of cool.  Not sure how I
get it to listen to the interface to dump packets, while at the same time
feeding snort with it in real time. I could have both Snort and
daemonlogger read from the same interface. However, I have been cautioned
by others and seen it myself that having 2 processes listening to the same
interface at the same time can cause competition which can cause packet
loss for one or both of the listening processes.  So I don't know if it is
permissible to have  both processes listening on the interface at the same
time.  Won't that just guarantee packet loss or is this not as much of
concern anymore with multiple core machines?





Thanks,



Kerry







*From:* Joel Esler (jesler) [mailto:jesler () cisco com]
*Sent:* Thursday, March 20, 2014 9:38 AM
*To:* Long, Kerry S
*Cc:* snort-users () lists sourceforge net
*Subject:* Re: [Snort-users] getting a full copy of pcap for forensic
purposes from Snort





On Mar 20, 2014, at 9:26 AM, Long, Kerry S <kslong () mitre org> wrote:



  I am trying to create a sensor with Snort that has Snort listening on
the interface processing rules and such while also creating a full copy of
pcap seen on the interface for forensic purposes.  I have enough storage to
hold about a month of pcap in this instance.  I am familiar with the
capability of using a log rule to log packets but the problem is that the
pcap has to go through all the alert rules first it seems before it can be
logged.  The problem is that packets can be dropped as the amount of
network traffic increases during the day.



I have tried using this in my config file to alleviate the problem:



# Per Packet latency configuration

config ppm: max-pkt-time 100, \

   fastpath-expensive-packets, \

   pkt-log



and this has helped somewhat but I am still not logging some packets
(which for a forensic record is bad) and I am missing the benefit of
several snort rules that take more than 100 usecs.





Any ideas how I can get Snort to both log all packets to disk and alert on
traffic it sees on the interface.



Daemonlogger is probably better for simply logging packets to disk, as it
has some capabilities that Snort does not:



http://sourceforge.net/projects/daemonlogger/



That way Snort can perform the IDS function and Daemonlogger can perform
the traffic logging function.



--
*Joel Esler*
Open Source Manager
Threat Intelligence Team Lead
Vulnerability Research Team


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applications. Written by three acclaimed leaders in the field,
this first edition is now available. Download your free book today!
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