Snort mailing list archives

A complication with an unconventional use of Snort


From: bahdko () erols com
Date: Tue, 19 Sep 2006 18:49:52 +0300

I have snort sensors deployed in an uncommon scenario, and I'm having a complication I'm hoping someone could give me 
input on.

The first part of the process does not experience problems. 

The data from the LAN is first gathered by a snort process that is run that just creates a binary file. The snort 
program that does this is started like so:

/usr/local/bin/snort -l /var/log/snort -bD -i eth1

This process results in a binary log file named something similar to snort.log.1126876613.

Then, when the Snort program has been restarted and the binary log file is closed, the second part of the process is as 
follows.

I use another instance of Snort to read this binary log file and re-log it into a fully-expanded ASCII format. An 
example command I use to do this is as follows:

/usr/local/bin/snort -dvCeq -K ascii -r /var/log/snort/snort.log.1126876613 net 192.168.10.0/24 -D -l 
/var/log/asciilogs/

The result of this operation is that there are directories within /var/log/asciilogs that contain all of the packet 
information, in ASCII, from the binary file.

My problem is this:

During this second instance of Snort, Snort appears to take the entire binary log file, no matter how big it is, and 
steadily read the whole thing into memory as it processes it. I can watch in "top" as the memory and swap available on 
the machine are steadily sucked away until the amount of memory displacing the binary file size are represented, and 
then the process ends and frees up the memory.

Does Snort really have to do it this way and take all of that memory? I know that Snort is processing this file 
sequentially, more or less packet-by-packet, it would seem that it shouldn't be necessary to hold the entire file in 
memory the whole time.

I periodically have some binary log files that exceed the swap+memory of my sensor, and I can't process those because 
of the way Snort is doing this.


Thanks,

--Laura




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