Splunk Search

Field Extraction - Trim Existing Field

jchampagne
Path Finder

In some of our event logs, the client IP address is recorded with leading information (::ffff:). I would like to trim this data and create a new field, which I can then do a reverse dns lookup on using a scripted lookup.

I'm not looking to modify the index, I'd like all of this to happen at search time.
The field I'm looking to modify is called Client_Address and a sample value would be:
::ffff:192.168.207.88

If I use the following REX at search time, I get a new field called Client_IP that looks good:
rex field=Client_Address "(?\b\d{1,3}.\d{1,3}.\d{1,3}.\d{1,3}\b)"

However, I'd like to use props.conf so this all happens automatically. If I add the following line to my WinEventLog:Security stanza, it doesn't work.

EXTRACT-ClientIP = rex field=Client_Address "(?\b\d{1,3}.\d{1,3}.\d{1,3}.\d{1,3}\b)"

0 Karma
1 Solution

MHibbin
Influencer

Firstly you don't need the rex part that is a search command.

You should look at the props.conf spec file.

Try something like

EXTRACT-ClientIP = [:,f]*(?<ip>\d+\.\d+\.\d+\.\d+)

OR

EXTRACT-ClientIP = [:,f]*(?<ip>\d{1,3}\.\{1,3}\.\d{1,3}\.\d{1,3})

Or you can just use the Interactive Field Extractor to help with the config of the props.conf (if you do the regex in IFX and save it, it will do the file itself.

View solution in original post

MHibbin
Influencer

Firstly you don't need the rex part that is a search command.

You should look at the props.conf spec file.

Try something like

EXTRACT-ClientIP = [:,f]*(?<ip>\d+\.\d+\.\d+\.\d+)

OR

EXTRACT-ClientIP = [:,f]*(?<ip>\d{1,3}\.\{1,3}\.\d{1,3}\.\d{1,3})

Or you can just use the Interactive Field Extractor to help with the config of the props.conf (if you do the regex in IFX and save it, it will do the file itself.

MHibbin
Influencer

no worries... what's with the "b" in your regex?

0 Karma

jchampagne
Path Finder

Thanks for the help!
I ended up using the following line, which seems to work.

EXTRACT-ClientIP = (?\b\d{1,3}.\d{1,3}.\d{1,3}.\d{1,3}\b)

0 Karma
Got questions? Get answers!

Join the Splunk Community Slack to learn, troubleshoot, and make connections with fellow Splunk practitioners in real time!

Meet up IRL or virtually!

Join Splunk User Groups to connect and learn in-person by region or remotely by topic or industry.

Get Updates on the Splunk Community!

Persistent Queue at TcpOut — One of Splunk's Most Practical Features

Splunk introduced persistent queueing at the tcpout layer as one of the most practical resilience features in ...

Skip the Awkward Silence: Have a .conf-ersation at .conf26

Picture this. You arrive at .conf26 already having your socializing and networking plans mapped out. No ...

Rethinking Zero Trust: From Product Purchases to Logical Control Evidence

Implementing Zero Trust (ZT) across complex environments often falters at the very beginning due to a ...