Kerberos key list attack for credential dumping

Status: experimental
Severity: high
Log source: product windows, service security
Author: mdecrevoisier
Source: github.com/mdecrevoisier/SIGMA-detection-rules

Detects scenarios where an attacker attempts to forge a special Kerberos service ticket in order to extract credentials from Read Only Domain Controllers (RODC).

Known false positives

Applications or services performing delegation activities, ADFS servers

MITRE ATT&CK coverage

Tactic	Techniques
Credential Access	`T1003` OS Credential Dumping `T1558` Steal or Forge Kerberos Tickets

Telemetry coverage

Provider	Record / event type
Security-Auditing	Event ID 4769: A Kerberos service ticket was requested.

Rule body

title: Kerberos key list attack for credential dumping
description: Detects scenarios where an attacker attempts to forge a special Kerberos service ticket in order to extract credentials from Read Only Domain Controllers (RODC).
references:
- https://www.secureauth.com/blog/the-kerberos-key-list-attack-the-return-of-the-read-only-domain-controllers/
- https://www.tarlogic.com/blog/how-to-attack-kerberos/
tags:
- attack.credential_access
- attack.t1003 # credential dumping
- attack.t1558 # forget ticket
author: mdecrevoisier
status: experimental
logsource:
  product: windows
  service: security
detection:
  selection:
    EventID: 4769
    Status: 0x0 # Success
    TicketOptions: '0x10000' # proxiable ticket
  filter:
    - IpAddress: '%domain_controllers_ips%'     # reduce amount of false positives
    - TargetUserName: '%account_allowed_proxy%' # accounts allowed to perform proxiable requests
  condition: selection and not filter
falsepositives:
- Applications or services performing delegation activities, ADFS servers
level: high

Stages and Predicates

Stage 0: `condition`

selection and not filter

Stage 1: `selection`

selection:
  EventID: 4769
  Status: 0x0
  TicketOptions: '0x10000'

Stage 2: `not filter`

filter:
  - IpAddress: '%domain_controllers_ips%'
  - TargetUserName: '%account_allowed_proxy%'

Exclusions

The rule actively suppresses these predicates.

Field	Kind	Excluded values	Search
`IpAddress`	eq	`%domain_controllers_ips%`	`excludes:IpAddress` `field:"IpAddress" value:"%domain_controllers_ips%"`
`TargetUserName`	eq	`%account_allowed_proxy%`	`excludes:TargetUserName` `field:"TargetUserName" value:"%account_allowed_proxy%"`

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`Status`	eq	`0` corpus 7 (sigma 7)	`field:"Status" kind:eq value:"0"`
`TicketOptions`	eq	`0x10000`	`field:"TicketOptions" kind:eq value:"0x10000"`