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Description

The following analytic identifies a computer account creating a new computer account with a specific Service Principal Name (SPN) "RestrictedKrbHost". This detection leverages Windows Security Event Logs, specifically EventCode 4741, to identify such activities. This behavior is significant as it may indicate an attempt to establish unauthorized Kerberos authentication channels, potentially leading to lateral movement or privilege escalation. If confirmed malicious, this activity could allow an attacker to impersonate services, access sensitive information, or maintain persistence within the network.

  • Type: TTP

  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud

  • Last Updated: 2024-05-20
  • 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 10
CVE 


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`wineventlog_security` EventCode=4741 user_type=computer SubjectDomainName!="NT AUTHORITY" ServicePrincipalNames=*RestrictedKrbHost* 
| stats  count min(_time) as firstTime max(_time) as lastTime by dest, subject, action ,src_user, user, user_type, SubjectUserName,SubjectDomainName 
| `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 on $dest$ created by a computer account (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: 3