Splunk Search

Why am I getting zero results using CIDR matching and a CSV lookup of IP subnets to scan through firewall logs for hits?

ltrand
Contributor

I'm attempting to use a CSV list of IP subnets to scan through firewall logs for hits, but it's not working out well.

lookup CSV is as follows:

address
"192.168.15.0/24"

transforms.conf looks like this:

[lan-ranges-test]
filename = lan-ranges-test.csv
match_type = CIDR(address)
fields_list = address

Attempted searches:
So far here is my search:

1:

sourcetype="firewalls"
| search [| inputlookup lan-ranges-test.csv | fields address | rename address as addresses]
| where cidrmatch(addresses, src)
|table src

2:

sourcetype="firewalls" src=*
| lookup lan-ranges-test.csv address as src OUTPUT address as sources
| search sources=* 
| table sources

These result in 0 hits. If I run the following search, however, I get hits:

sourcetype="firewalls" src="192.168.15.0/24"

Any thoughts on why I can't get the CSV to work? I have hundreds that I'd like to not have to export raw logs and go excel ninja on.

Thanks!

0 Karma
1 Solution

ltrand
Contributor

Figured it out, pretty simple I was just nuking it:
sourcetype="firewalls" | fields src, dest, action
| search [| inputlookup lan-ranges.csv | fields address | rename address as src]
| dedup src,dest
|table src, dest, action

View solution in original post

0 Karma

ltrand
Contributor

Figured it out, pretty simple I was just nuking it:
sourcetype="firewalls" | fields src, dest, action
| search [| inputlookup lan-ranges.csv | fields address | rename address as src]
| dedup src,dest
|table src, dest, action

0 Karma

ltrand
Contributor

Get's even weirder:

when attempting the following:

sourcetype="firewalls" | where cidrmatch([| inputlookup lan-ranges-test.csv | fields address],src_ip) | stats values(dest_port) AS DST_Port by src_ip,transport

I get the following error:
Error in 'where' command: The arguments to the 'cidrmatch' function are invalid.

0 Karma
Get Updates on the Splunk Community!

Upcoming Webinar: Unmasking Insider Threats with Slunk Enterprise Security’s UEBA

Join us on Wed, Dec 10. at 10AM PST / 1PM EST for a live webinar and demo with Splunk experts! Discover how ...

.conf25 technical session recap of Observability for Gen AI: Monitoring LLM ...

If you’re unfamiliar, .conf is Splunk’s premier event where the Splunk community, customers, partners, and ...

A Season of Skills: New Splunk Courses to Light Up Your Learning Journey

There’s something special about this time of year—maybe it’s the glow of the holidays, maybe it’s the ...