windows_large_number_of_computer_service_tickets_requested.yml

name: Windows Large Number of Computer Service Tickets Requested
id: 386ad394-c9a7-4b4f-b66f-586252de20f0
version: 1
date: '2023-03-20'
author: Mauricio Velazco, Splunk
type: Anomaly
status: production
data_source:
- Windows Event Log Security 4769
description: The following analytic leverages Event ID 4769, `A Kerberos
  service ticket was requested`, to identify more than 30 computer service
  ticket requests from one source. When a domain joined endpoint connects to other remote
  endpoint, it will first request a Kerberos Service Ticket with the computer name as the
  Service Name. A user requesting a large number of computer service tickets
  for different endpoints could represent malicious behavior like lateral movement,
  malware staging, reconnaissance, etc.

  Active Directory environments can be very different depending on the organization. Users should test this detection and customize 
  the arbitrary threshold as needed.

search: ' `wineventlog_security` EventCode=4769 ServiceName="*$" TargetUserName!="*$"
  | bucket span=5m _time 
  | stats dc(ServiceName) AS unique_targets values(ServiceName) as host_targets by _time, IpAddress, TargetUserName
  | where unique_targets > 30
  | `windows_large_number_of_computer_service_tickets_requested_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: An single endpoint requesting a large number of kerberos service tickets is not common behavior.
  Possible false positive scenarios include but are not limited to vulnerability scanners, administration systems and missconfigured systems.
references:
- https://thedfirreport.com/2023/01/23/sharefinder-how-threat-actors-discover-file-shares/
- https://attack.mitre.org/techniques/T1135/
- https://learn.microsoft.com/en-us/windows/security/threat-protection/auditing/event-4769
tags:
  analytic_story:
  - Active Directory Privilege Escalation
  - Active Directory Lateral Movement
  asset_type: Endpoint
  confidence: 50
  impact: 60
  message: A large number of kerberos computer service tickets were requested by $IpAddress$ within 5 minutes.
  mitre_attack_id:
  - T1135
  - T1078
  observable:
  - name: IpAddress
    type: Endpoint
    role:
    - Victim
  product:
  - Splunk Enterprise
  - Splunk Enterprise Security
  - Splunk Cloud
  required_fields:
  - _time
  - EventCode
  - ServiceName
  - TargetUserName
  - IpAddress
  risk_score: 30
  security_domain: endpoint
tests:
- name: True Positive Test
  attack_data:
  - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1135/large_number_computer_service_tickets/windows-security.log
    source: XmlWinEventLog:Security
    sourcetype: XmlWinEventLog