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Description

The following analytic identifes a Computer Account creating a new Computer Account with specific a Service Principle Name - "RestrictedKrbHost". The RestrictedKrbHost service class allows client applications to use Kerberos authentication when they do not have the identity of the service but have the server name.

  • Type: TTP
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Endpoint
  • Last Updated: 2022-04-27
  • Author: Michael Haag, Splunk
  • ID: 97a8dc5f-8a7c-4fed-9e3e-ec407fd0268a

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 3
  • CIS 5
  • CIS 16
CVE
1
2
3
4
5
`wineventlog_security` EventCode=4741 user_type=computer Subject_Account_Domain!="NT AUTHORITY"  Message=*RestrictedKrbHost* 
| stats  count min(_time) as firstTime max(_time) as lastTime by dest, subject, action ,src_user, user, Account_Name, Subject_Account_Name,Subject_Account_Domain 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `windows_computer_account_created_by_computer_account_filter`

Macros

The SPL above uses the following Macros:

:information_source: windows_computer_account_created_by_computer_account_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
  • dest
  • subject
  • action
  • src_user
  • user
  • Account_Name
  • Subject_Account_Name
  • Subject_Account_Domain

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 have a computer account that adds computer accounts, filtering may be required.

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
30.0 50 60 A Computer Account created a Computer Account 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

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