Windows Multiple Invalid Users Fail To Authenticate Using Kerberos

name: Windows Multiple Invalid Users Fail To Authenticate Using Kerberos
id: 001266a6-9d5b-11eb-829b-acde48001122
date: '2026-03-10'
version: 10
type: TTP
status: production
author: Mauricio Velazco, Splunk
data_source:
    - Windows Event Log Security 4768
description: The following analytic identifies a source endpoint failing to authenticate with 30 unique invalid domain users using the Kerberos protocol. This detection leverages EventCode 4768, specifically looking for failure code 0x6, indicating the user is not found in the Kerberos database. This activity is significant as it may indicate a Password Spraying attack, where an adversary attempts to gain initial access or elevate privileges. If confirmed malicious, this could lead to unauthorized access or privilege escalation within the Active Directory environment, posing a significant security risk.
how_to_implement: To successfully implement this search, you need to be ingesting Domain Controller and Kerberos events. The Advanced Security Audit policy setting `Audit Kerberos Authentication Service` within `Account Logon` needs to be enabled.
known_false_positives: A host failing to authenticate with multiple invalid domain users is not a common behavior for legitimate systems. Possible false positive scenarios include but are not limited to vulnerability scanners, multi-user systems and missconfigured systems.
references:
    - https://attack.mitre.org/techniques/T1110/003/
drilldown_searches:
    - name: View the detection results for - "$user$"
      search: '%original_detection_search% | search  user = "$user$"'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
    - name: View risk events for the last 7 days for - "$user$"
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$user$") starthoursago=168  | 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: $info_min_time$
      latest_offset: $info_max_time$
search: |-
    `wineventlog_security` EventCode=4768 TargetUserName!=*$ Status=0x6
      | bucket span=5m _time
      | stats dc(TargetUserName) AS unique_accounts values(TargetUserName) as user values(dest) as dest
        BY _time, IpAddress
      | where unique_accounts > 30
      | `windows_multiple_invalid_users_fail_to_authenticate_using_kerberos_filter`
rba:
    message: Potential Kerberos based password spraying attack from $IpAddress$
    risk_objects:
        - field: user
          type: user
          score: 50
    threat_objects:
        - field: IpAddress
          type: ip_address
tags:
    analytic_story:
        - Active Directory Password Spraying
        - Active Directory Kerberos Attacks
        - Volt Typhoon
    asset_type: Endpoint
    mitre_attack_id:
        - T1110.003
    product:
        - Splunk Enterprise
        - Splunk Enterprise Security
        - Splunk Cloud
    security_domain: endpoint
tests:
    - attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1110.003/purplesharp_invalid_users_kerberos_xml/windows-security.log
          source: XmlWinEventLog:Security
          sourcetype: XmlWinEventLog
      name: True Positive Test