Snort mailing list archives
Re: Odd bug when using alert_json plugin
From: Noah Dietrich <noah_dietrich () 86penny org>
Date: Sat, 16 Jun 2018 11:37:08 +0200
Ok, i think I've figured out what's going on with this issue, but I'm not sure it's a good idea the way things are working. What seems to happen is when you start Snort3, it begins filling the alert_json.txt file. Once that file hits the limit (say 100 MB), Snort re-names this file to alert_json.txt.nnnnnnnnnn, where the n's represent the unixtime of when the file was re-named. Snort then creates a new alert_json.txt file (without the unixtime), and continues to write new events to that file. The issues i see with this method of rollover are that log-monitoring programs won't be expecting file names to change. So i'd be forced to only consume only log files with the unixtime portion, meaning i wouldn't get to consume new events until the log rolled over. If i consumed events from the original file, there is a good chance that i'd also re-consume (duplicate) those events again when the filename was renamed. My request is that when snort starts, it just outputs it's events to a new file, with the unixtime appended to the filename( alert_json.txt.nnnnnnnnnn) , and not output to alert_json.txt at any time, and especially not rename files. This will ensure that there are no issues ingesting this data into SIEMs like Splunk or the ELK stack. Thank you, Noah On Wed, Jun 13, 2018 at 9:20 AM, Noah Dietrich <noah_dietrich () 86penny org> wrote:
I'm playing around with the alert_json plugin, and i found a bit of odd behavior. When running snort in alert mode, it correctly created the /var/log/snort/alert_json.txt file and filled it with events (about 17 MB of data in that file). I then restarted snort and pushed a huge amount of data at it (sudo ping -c 10000 -i .001 -s 4046 10.0.0.106), and snort created a new file with the timestamp (alert_json.txt.1528868120), even though the first file hadn't filled up and filled it with 100 MB of data. I then re-ran snort, with a smaller dataset from local pcaps, and it appended the events to the original alert_json.txt file. I'd call this an odd bug because most applications that consume the json files will ignore the first file once the second file is created. I'd say there are two issues here: 1. Snort rolled over to the second json file early, before the original one (without the timestamp) was full. I'm not sure if this was because of the large ammount of data i threw at it with the ping command above. 2. snort appended alert data to the original alert_json file because it wasn't full, even though there was a newer (by UTC timestamp) json file in the directory. i'd recommend that snort not create an initial alert_json file without a timestamp if no alert_json files exist, just so there are no differences between the output files. I am running snort with community rules installed (unmodified), two of my own local rules (one that alerts on icmp traffic), and builtin rules enabled. First run: sudo snort -c /usr/local/etc/snort/snort.lua --pcap-filter \*.pcap --pcap-dir ~/snort_src/Pcaps -R /usr/local/etc/snort/rules/snort3-community.rules -A alert_json -s 65535 -k none -l /var/log/snort Second run: sudo snort -c /usr/local/etc/snort/snort.lua -i ens160 -l /var/log/snort -A alert_json -R /usr/local/etc/snort/rules/snort3-community.rules --warn-all third run: sudo snort -c /usr/local/etc/snort/snort.lua -r ~/maccdc2012_00000.pcap -R /usr/local/etc/snort/rules/snort3-community.rules -A alert_json -s 65535 -k none -l /var/log/snort (note: pcap from https://download.netresec.com/pcap/maccdc-2012/ maccdc2012_00000.pcap.gz)
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Current thread:
- Odd bug when using alert_json plugin Noah Dietrich (Jun 13)
- Re: Odd bug when using alert_json plugin Noah Dietrich (Jun 16)
- Re: Odd bug when using alert_json plugin Russ via Snort-devel (Jun 17)
- Re: Odd bug when using alert_json plugin Noah Dietrich (Jun 16)