Potential Kerberos Coercion by Spoofing SPNs via DNS Manipulation

Status: experimental
Severity: high
Log source: product windows, service security
Author: Swachchhanda Shrawan Poudel (Nextron Systems)
Source: github.com/SigmaHQ/sigma

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.

MITRE ATT&CK coverage

Tactic	Techniques
Credential Access	`T1557.003` Adversary-in-the-Middle: DHCP Spoofing
Collection	`T1557.003` Adversary-in-the-Middle: DHCP Spoofing

Event coverage

Provider	Event	Title
Security-Auditing	Event ID 4662	An operation was performed on an object.
Security-Auditing	Event ID 5136	A directory service object was modified.
Security-Auditing	Event ID 5137	A directory service object was created.

Rule body yaml

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

Stages and Predicates

Stage 0: `condition`

1 of selection_*

Stage 1: `selection_directory_service_changes`

selection_directory_service_changes:
    EventID:
        - 5136
        - 5137
    ObjectClass: 'dnsNode'
    ObjectDN|contains|all:
        - 'UWhRCA'
        - 'BAAAA'
        - 'CN=MicrosoftDNS'

Stage 2: `selection_directory_service_access`

selection_directory_service_access:
    EventID: 4662
    AdditionalInfo|contains|all:
        - 'UWhRCA'
        - 'BAAAA'
        - 'CN=MicrosoftDNS'

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

Field	Kind	Values
`AdditionalInfo`	match	`BAAAA` `CN=MicrosoftDNS` `UWhRCA`
`ObjectClass`	eq	`dnsNode` corpus 4 (splunk 2, sigma 1, elastic 1)
`ObjectDN`	match	`BAAAA` `CN=MicrosoftDNS` `UWhRCA`

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`type:`	`events` / `rules` / `providers`
`vendor:`	`sigma` / `elastic` / `splunk` / `kusto` / `chronicle` (vendor name alone also works: `sigma:`, `kql:`, `secops:`…)
`tactic:`	TA-id, slug, or name: `credential_access`, `TA0006`
`technique:`	technique or sub-technique ID: `T1003`, `T1003.001` (alias `tech:`)
`severity:`	`critical` / `high` / `medium` / `low` / `informational` (alias `sev:`)
`risk_score`	Numeric comparison on the Elastic risk score (0 to 100): `risk_score>50`, `risk_score<=20`, `risk_score=99` (alias `risk`; Elastic rules only)
`stages:`	Rules with exactly N pipeline stages
`correlation:`	`single_event` / `sequence` / `alternatives` / `alternatives_cross_log` / `all_required` / `correlated`
`with:`	Co-occurrence event-id; stacks (`with:4624 with:4769`) to require all, while a comma list in one occurrence (`with:4624,4769`) is an either-or group. Implies multi-event
`like:`	Structural neighbors of a rule slug (equivalents + subsumption stricter / broader): `like:comsvcs_lsass_memory_dump-splunk-sysmon`
`groupby:`	Entity-grouping substring match against `group_by_keys`: `groupby:user`, `groupby:host`
`uses:`	Rules whose predicate tree touches the field (any kind, any value): `uses:CommandLine`
`excludes:`	Rules with top-level `not()` clauses on the field (FP whitelists): `excludes:ParentImage`
`field:` / `value:`	Predicate search; narrows rule cards to those with a matching leaf and drives the indicator tier. Unquoted = substring, wildcards allowed (`value:mimikatz`)
`indicator:`	Shorthand for `field:F value:V`: `indicator:Image=*\powershell.exe`
`kind:`	Filter by predicate kind. Narrows rule cards to those carrying a matching predicate leaf (`vendor:elastic kind:cidr_match`) and drives the indicator tier: `contains` / `starts_with` / `ends_with` / `regex` / `cidr` / `eq` / `in` … (operator aliases `op:`/`match:`)
`has:` / `no:`	`sample`, `field`, `notes`, `refs`, `trace`, `thirdparty`, `rule`, `pattern`, `timewindow`, `threshold`, `newterms`, `sigma`/`elastic`/`splunk`/`kusto`/`chronicle`
`-op:val`	Exclude matches; works on most operators but not `type:`/`like:`/`has:`/`no:` (use `no:<flag>` to exclude a rule flag): `tactic:execution -vendor:splunk`. Standalone `-kind:`/`-field:`/`-value:` drop every rule carrying a matching predicate leaf (`type:rules -kind:is_null`)
`field:"…"` / `value:"…"`	Quoted value = anchored exact match (also allows spaces): `value:"net user"`
`a,b`	Comma = OR inside one operator (`vendor:sigma,elastic`, `severity:high,critical`); repeating a facet merges the same way. `field:`/`value:` never split (literal commas)
`vendors:` / `stage:`	Singular and plural spellings fold to the canonical operator and value: `tactics:` = `tactic:`, `type:event` = `type:events`, `correlation:sequences` = `correlation:sequence`, `has:thresholds` = `has:threshold`
`"quoted phrase"`	Exact-match a multi-word phrase (free text)

Potential Kerberos Coercion by Spoofing SPNs via DNS Manipulation

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: `condition`

Stage 1: `selection_directory_service_changes`

Stage 2: `selection_directory_service_access`

Indicators

Keyboard shortcuts

Search operators

Potential Kerberos Coercion by Spoofing SPNs via DNS Manipulation

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: condition

Stage 1: selection_directory_service_changes

Stage 2: selection_directory_service_access

Indicators

Stage 0: `condition`

Stage 1: `selection_directory_service_changes`

Stage 2: `selection_directory_service_access`