Potential Kerberos Coercion by Spoofing SPNs via DNS Manipulation — Sigma Rule

Rule metadata and linked tags

Author: Swachchhanda Shrawan Poudel (Nextron Systems). Source status: experimental; severity: high. Source dates: 2025-06-20 / not supplied.

{
  "product": "windows",
  "service": "security",
  "definition": "By default these events are not logged by default for MicrosoftDNS objects in Active Directory.\nTo enable detection, configure an AuditRule on the DNS object container with the \"CreateChild\" permission for the \"Everyone\" principal.\nThis can be accomplished using tools such as Set-AuditRule (see https://github.com/OTRF/Set-AuditRule).\n"
}

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 0ef61cfa37bd698b5c7db966bbb146420026443c20731702e2fc97008b4e4619

Detection logic

Original source YAML. Source-tag agreement is not proof of complete semantic coverage. This rule has not been compiled for a SIEM backend or validated against live telemetry here.

title: Potential Kerberos Coercion by Spoofing SPNs via DNS Manipulation
id: b07e58cf-cacc-4135-8473-ccb2eba63dd2
related:
    - id: e7a21b5f-d8c4-4ae5-b8d9-93c5d3f28e1c # Suspicious DNS Query Indicating Kerberos Coercion via DNS Object Spoofing
      type: similar
    - id: 5588576c-5898-4fac-bcdd-7475a60e8f43 # Suspicious DNS Query Indicating Kerberos Coercion via DNS Object Spoofing - Network
      type: similar
    - id: 0ed99dda-6a35-11ef-8c99-0242ac120002 # Kerberos Coercion Via DNS SPN Spoofing Attempt
      type: similar
status: experimental
description: |
    Detects modifications to DNS records in Active Directory where the Distinguished Name (DN) contains a base64-encoded blob
    matching the pattern "1UWhRCAAAAA...BAAAA". This pattern corresponds to a marshaled CREDENTIAL_TARGET_INFORMATION structure,
    commonly used in Kerberos coercion attacks. Adversaries may exploit this to coerce victim systems into authenticating to
    attacker-controlled hosts by spoofing SPNs via DNS. It is one of the strong indicators of a Kerberos coercion attack,.
    where adversaries manipulate DNS records to spoof Service Principal Names (SPNs) and redirect authentication requests like CVE-2025-33073.
    Please investigate the user account that made the changes, as it is likely a low-privileged account that has been compromised.
references:
    - https://googleprojectzero.blogspot.com/2021/10/using-kerberos-for-authentication-relay.html
    - https://www.synacktiv.com/publications/ntlm-reflection-is-dead-long-live-ntlm-reflection-an-in-depth-analysis-of-cve-2025
author: Swachchhanda Shrawan Poudel (Nextron Systems)
date: 2025-06-20
tags:
    - attack.collection
    - attack.credential-access
    - attack.t1557.003
    - attack.persistence
    - attack.privilege-escalation
logsource:
    product: windows
    service: security
    definition: |
      By default these events are not logged by default for MicrosoftDNS objects in Active Directory.
      To enable detection, configure an AuditRule on the DNS object container with the "CreateChild" permission for the "Everyone" principal.
      This can be accomplished using tools such as Set-AuditRule (see https://github.com/OTRF/Set-AuditRule).
detection:
    selection_directory_service_changes:
        EventID:
            - 5136
            - 5137
        ObjectClass: 'dnsNode'
        ObjectDN|contains|all: # ObjectDN">DC=foo-11UWhRCAAAAAAAAAAAAAAAAAAAAAAAAAAAAwbEAYBAAAA,DC=domain.com,CN=MicrosoftDNS,DC=DomainDnsZones,DC=domain,DC=com</Data>
            - 'UWhRCA'
            - 'BAAAA'
            - 'CN=MicrosoftDNS'
    selection_directory_service_access:
        EventID: 4662
        AdditionalInfo|contains|all: # AdditionalInfo">DC=foo-11UWhRCAAAAAAAAAAAAAAAAAAAAAAAAAAAAwbEAYBAAAA,DC=domain.com,CN=MicrosoftDNS,DC=DomainDnsZones,DC=domain,DC=com</Data>
            - 'UWhRCA'
            - 'BAAAA'
            - 'CN=MicrosoftDNS'
    condition: 1 of selection_*
falsepositives:
    - Unknown
level: high

Original YAML and metadata in JSON

False positives

• Unknown

Source references

• https://googleprojectzero.blogspot.com/2021/10/using-kerberos-for-authentication-relay.html
• https://www.synacktiv.com/publications/ntlm-reflection-is-dead-long-live-ntlm-reflection-an-in-depth-analysis-of-cve-2025