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Description

The following analytic identifies two SPNs, HOST and RestrictedKrbHost, added using the KrbRelayUp behavior. This particular behavior has been found in other Kerberos based attacks.

  • Type: TTP
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Change
  • Last Updated: 2022-04-28
  • Author: Michael Haag, Splunk
  • ID: 9a3e57e7-33f4-470e-b25d-165baa6e8357

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1558 Steal or Forge Kerberos Tickets Credential Access
Kill Chain Phase
  • Exploitation
NIST
  • DE.CM
CIS20
  • CIS 10
CVE 


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`wineventlog_security` EventCode=4741 MSADChangedAttributes IN ("*HOST/*","*RestrictedKrbHost/*") AND New_UAC_Value=0x80 
| eval Effecting_Account=mvindex(Security_ID,1) 
| eval New_Computer_Account_Name=mvindex(Security_ID,0) 
| stats count min(_time) as firstTime max(_time) as lastTime values(EventCode),values(Account_Domain),values(Security_ID), values(Effecting_Account), values(New_Computer_Account_Name),values(SAM_Account_Name),values(DNS_Host_Name),values(MSADChangedAttributes) by dest Logon_ID subject 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `windows_computer_account_with_spn_filter`

Macros

The SPL above uses the following Macros:

:information_source: windows_computer_account_with_spn_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required fields

List of fields required to use this analytic.

  • _time
  • EventCode
  • MSADChangedAttributes
  • New_UAC_Value
  • Security_ID
  • Account_Domain
  • SAM_Account_Name
  • DNS_Host_Name
  • Logon_Id

How To Implement

To successfully implement this search, you need to be ingesting Windows Security Event Logs with 4741 EventCode enabled. The Windows TA is also required.

Known False Positives

It is possible third party applications may add these SPNs to Computer Accounts, filtering may be needed.

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
64.0 80 80 A Computer Account was created with SPNs related to Kerberos on $dest$, possibly indicative of Kerberos relay attack.

:information_source: The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

Reference

Test Dataset

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

source | version: 1