DC Machine Account Network Logon from Non-DC Source IP

title: DC Machine Account Network Logon from Non-DC Source IP
id: b2e4a719-3c8f-4d1b-a507-f83c2d56e901
status: experimental
description: |
    Detects a Domain Controller machine account authenticating from a source IP that is not
    a known Domain Controller. DC machine accounts should only authenticate locally or from other DCs during
    replication operations. Any logon event for a DC account from a workstation or non-DC host is anomalous and
    indicates one of the following:

      - Silver Ticket: attacker forged a Kerberos TGS for a DC machine account without
        requesting a TGT
      - Pass-the-Ticket: attacker is replaying a captured DC machine account TGS from
        a non-DC host
      - Overpass-the-Hash: attacker converted a stolen DC machine account hash into a
        Kerberos ticket and is authenticating from a non-DC host
      - Exploitation of certain vulnerabilities such as CVE-2026-54121 (Certighost):
        attacker obtained a DC certificate via ADCS CDC-chase
        abuse, authenticates via PKINIT as the DC from their own host, then performs DCSync
references:
    - https://github.com/aniqfakhrul/CVE-2026-54121
author: Swachchhanda Shrawan Poudel (Nextron Systems)
date: 2026-07-29
tags:
    - attack.credential-access
    - attack.lateral-movement
    - attack.t1550.003
    - attack.t1558.002
    - attack.t1649
    - cve.2026-54121
logsource:
    product: windows
    service: security
detection:
    selection:
        EventID: 4624
        TargetUserName|endswith: '$'
        TargetUserName|expand: '%dc_machine_accounts%'
    filter_main_dc_source:
        IpAddress|expand: '%dc_ip_addresses%'
    filter_main_loopback:
        - IpAddress:
              - '127.0.0.1'
              - '::1'
              - '::ffff:127.0.0.1'
              - '-'
        - IpAddress|startswith: 'fe80:'
    condition: selection and not 1 of filter_main_*
falsepositives:
    - Unlikely if %dc_machine_accounts% and %dc_ip_addresses% are correctly populated.
level: critical