Windows Computer Account With SPN

Description

The following analytic detects the addition of Service Principal Names (SPNs) HOST and RestrictedKrbHost to a computer account, indicative of KrbRelayUp behavior. This detection leverages Windows Security Event Logs, specifically EventCode 4741, to identify changes in SPNs. This activity is significant as it is commonly associated with Kerberos-based attacks, which can be used to escalate privileges or perform lateral movement within a network. If confirmed malicious, this behavior could allow an attacker to impersonate services, potentially leading to unauthorized access to sensitive resources.

Query · spl

`wineventlog_security` EventCode=4741 NewUacValue="0x80" ServicePrincipalNames IN ("*HOST/*","*RestrictedKrbHost/*")
  | stats count min(_time) as firstTime max(_time) as lastTime values(EventCode),values(TargetDomainName),values(PrimaryGroupId), values(OldUacValue), values(NewUacValue),values(SamAccountName),values(DnsHostName),values(ServicePrincipalNames)
    BY dest Logon_ID subject
  | `security_content_ctime(firstTime)`
  | `security_content_ctime(lastTime)`
  | `windows_computer_account_with_spn_filter`

Implementation guide

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.

Analyst notes

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

Raw source Windows Computer Account With SPN · SPL
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Published by splunk/security_content ↗, licensed under Apache 2.0 ↗. Reproduced here unmodified. 
name: Windows Computer Account With SPN
id: 9a3e57e7-33f4-470e-b25d-165baa6e8357
version: 11
creation_date: '2022-04-28'
modification_date: '2026-05-13'
author: Michael Haag, Splunk
status: production
type: TTP
description: The following analytic detects the addition of Service Principal Names (SPNs) HOST and RestrictedKrbHost to a computer account, indicative of KrbRelayUp behavior. This detection leverages Windows Security Event Logs, specifically EventCode 4741, to identify changes in SPNs. This activity is significant as it is commonly associated with Kerberos-based attacks, which can be used to escalate privileges or perform lateral movement within a network. If confirmed malicious, this behavior could allow an attacker to impersonate services, potentially leading to unauthorized access to sensitive resources.
data_source:
    - Windows Event Log Security 4741
search: |-
    `wineventlog_security` EventCode=4741 NewUacValue="0x80" ServicePrincipalNames IN ("*HOST/*","*RestrictedKrbHost/*")
      | stats count min(_time) as firstTime max(_time) as lastTime values(EventCode),values(TargetDomainName),values(PrimaryGroupId), values(OldUacValue), values(NewUacValue),values(SamAccountName),values(DnsHostName),values(ServicePrincipalNames)
        BY dest Logon_ID subject
      | `security_content_ctime(firstTime)`
      | `security_content_ctime(lastTime)`
      | `windows_computer_account_with_spn_filter`
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.
references:
    - https://www.trustedsec.com/blog/an-attack-path-mapping-approach-to-cves-2021-42287-and-2021-42278
    - https://github.com/Dec0ne/KrbRelayUp
drilldown_searches:
    - name: View the detection results for - "$dest$"
      search: '%original_detection_search% | search  dest = "$dest$"'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
    - name: View risk events for the last 7 days for - "$dest$"
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$dest$") | stats count min(_time) as firstTime max(_time) as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk Message" values(analyticstories) as "Analytic Stories" values(annotations._all) as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics" by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`'
      earliest_offset: 7d
      latest_offset: "0"
finding:
    title: A Computer Account was created with SPNs related to Kerberos on $dest$, possibly indicative of Kerberos relay attack.
    entity:
        field: dest
        type: system
        score: 50
analytic_story:
    - Local Privilege Escalation With KrbRelayUp
    - Active Directory Kerberos Attacks
    - Compromised Windows Host
asset_type: Endpoint
mitre_attack_id:
    - T1558
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: endpoint
security_domain: endpoint
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1558/windows_computer_account_with_spn/windows-xml.log
          source: XmlWinEventLog:Security
          sourcetype: XmlWinEventLog
      test_type: unit

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