[Snort-users] Drifting timestamps

Jacob Roberts jake_roberts at ...10077...
Mon Oct 18 12:19:03 EDT 2004

We check the timezones and clocks of all the systems involved.  They are
all correct and don't drift from day to day.

They daily routine is to Stop barnyard, stop snort, drop the Mysql
database(not just deleted the records), re-create the database, start
snort, start barnyard.

At the time everything is restarted the timestamps are in sync with
correct time.  As the system runs the timestamps drift

We've narrowed it down to on of the following:
	1. Something weird in Snort (probably not)
	2. Something in Barnyard (we've no idea)
	3. Something in Mysql. (We've added a timestamp column to the
event table and it auto-inserted correct timestamps. So we don't thing
its Mysql)

Could this be a Barnyard thing?

-----Original Message-----
From: Martin Roesch [mailto:roesch at ...1935...] 
Sent: Sunday, October 17, 2004 9:10 AM
To: Jacob Roberts
Cc: snort-users at lists.sourceforge.net
Subject: Re: [Snort-users] Drifting timestamps

Hi Jake,

That'd have to be the system clock on the sensor drifting, the 
timestamps that Snort uses is based on a call to gettimeofday() that 
libpcap performs when it receives a new packet.  Snort has no internal 
time tracking mechanisms and in fact we take advantage of the fact that 
libpcap gives us time data "for free" to track time inside Snort.


On Oct 15, 2004, at 6:50 PM, Jacob Roberts wrote:

> We have a snort setup with barnyard which dumps in to a MySQL 
> database. We stop snort and barnyard each day, delete the database, 
> re-create it, then restart snort and barnyard.
> As snort runs through the day we start to see the timestamps of alerts

> drift behind actual time.  We aren't receiving an excessive amount of 
> alerts so we ruled out Barnyard not being able to keep up with the 
> alerts generated by Snort (I don't know if that would happen anyways)
> Has anyone had anything like this happen?  We haven't been able to
> track
> it down and aren't sure what to do.
> Thanks,
> Jake Roberts
> Brigham Young University
> jake_roberts at ...10077...
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Martin Roesch - Founder/CTO, Sourcefire Inc. - +1-410-290-1616
Sourcefire - Discover.  Determine.  Defend. roesch at ...1935... -
Snort: Open Source Network IDS - http://www.snort.org

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