Splunk Enterprise Security

Separating Kerberos Events in Datamodel.Authentication



Kerberos will attempt to impersonate a user by requesting tickets from the Domain Controllers on any domain joined computers OR if a user is logging into a .NET web service, this generates a LOT of noise and triggers our Brute Force, Excessive Login, and Geographically Improbable Access notables.
The goal is to clean-up and/or suppress Notable Events within Enterprise Security that are related to Kerberos.

Looking at:

 |from datamodel:"Authentication"."Authentication" | search kerberos

We see that each kerberos logon process contains 3 event codes AS signature_id:



For the latter two,

TaskCategory=Kerberos Service Ticket Operations

TaskCategory=Kerberos Authentication Service

I can modify the Correlation Searches to filter event 4768 or 4769 as they relate exclusively to Kerberos.

| `tstats` min(_time),earliest(Authentication.app) from datamodel=Authentication.Authentication where Authentication.action="success" AND Authentication.signature_id!="4768" AND Authentication.signature_id!="4768"  by Authentication.src,Authentication.user [...and so forth...]

The issue:
Events 4624 are generated for ANY logon event, kerberos or otherwise.
Looking at a RAW event, I see that 4624: contains a field: Logon Process: Kerberos:

Detailed Authentication Information:
    Logon Process:      Kerberos
    Authentication Package: Kerberos
    Transited Services:
    Package Name (NTLM only):
    Key Length:     0

This is properly extracted on index="wineventlog:security" but does not seem to be so when we do a search against the datamodel (which is primarily CIM fields).

How else can I isolate these events and use them in Correlation Searches?

0 Karma


If you don't need Logon Process: Kerberos events, you can filter them in the universal forwarder on the windows server using blacklist to filter 4624 with kerberos.

On the other hand, if you do not want to filter them (as they may be required for forensics/analysis of auth processes during incident), you can define a custom field in the Authentication datamodel and map logon process which can be used to filter in your tstats search .

0 Karma
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