Kerberos User Enumeration

name: Kerberos User Enumeration
id: d82d4af4-a0bd-11ec-9445-3e22fbd008af
version: 13
creation_date: '2022-03-11'
modification_date: '2026-05-13'
author: Mauricio Velazco, Splunk
status: production
type: Anomaly
description: The following analytic detects an unusual number of Kerberos Ticket Granting Ticket (TGT) requests for non-existing users from a single source endpoint. It leverages Event ID 4768 and identifies anomalies using the 3-sigma statistical rule. This behavior is significant as it may indicate an adversary performing a user enumeration attack against Active Directory. If confirmed malicious, the attacker could validate a list of usernames, potentially leading to further attacks such as brute force or credential stuffing, compromising the security of the environment.
data_source:
    - Windows Event Log Security 4768
search: |-
    `wineventlog_security` EventCode=4768 Status=0x6 TargetUserName!="*$"
      | bucket span=2m _time
      | stats dc(TargetUserName) AS unique_accounts values(TargetUserName) as tried_accounts values(dest) as dest
        BY _time, src_ip
      | eventstats avg(unique_accounts) as comp_avg , stdev(unique_accounts) as comp_std
        BY src_ip
      | eval upperBound=(comp_avg+comp_std*3)
      | eval isOutlier=if(unique_accounts > 10 and unique_accounts >= upperBound, 1, 0)
      | search isOutlier=1
      | `kerberos_user_enumeration_filter`
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: Possible false positive scenarios include but are not limited to vulnerability scanners and missconfigured systems.
references:
    - https://github.com/ropnop/kerbrute
    - https://attack.mitre.org/techniques/T1589/002/
    - https://redsiege.com/tools-techniques/2020/04/user-enumeration-part-3-windows/
intermediate_findings:
    entities:
        - field: src_ip
          type: system
          score: 20
          message: Potential Kerberos based user enumeration attack $src_ip$
analytic_story:
    - Active Directory Kerberos Attacks
asset_type: Endpoint
mitre_attack_id:
    - T1589.002
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: endpoint
security_domain: endpoint