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Description

The following analytic detects Kerberos service ticket requests using RC4 encryption, leveraging Kerberos Event 4769. This method identifies potential Golden Ticket attacks, where adversaries forge Kerberos Granting Tickets (TGT) using the Krbtgt account NTLM password hash to gain unrestricted access to an Active Directory environment. Monitoring for RC4 encryption usage is significant as it is rare in modern networks, indicating possible malicious activity. If confirmed malicious, attackers could move laterally and execute code on remote systems, compromising the entire network. Note: This detection may be bypassed if attackers use the AES key instead of the NTLM hash.

  • Type: TTP

  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud

  • Last Updated: 2024-05-27
  • Author: Mauricio Velazco, Splunk
  • ID: 7d90f334-a482-11ec-908c-acde48001122

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1558 Steal or Forge Kerberos Tickets Credential Access
T1558.001 Golden Ticket Credential Access
Kill Chain Phase
  • Exploitation
NIST
  • DE.CM
CIS20
  • CIS 10
CVE 


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 `wineventlog_security` EventCode=4769 ServiceName="*$" (TicketOptions=0x40810000 OR TicketOptions=0x40800000 OR TicketOptions=0x40810010) TicketEncryptionType=0x17 
| stats count min(_time) as firstTime max(_time) as lastTime by dest, service, service_id, TicketEncryptionType, TicketOptions 
| `security_content_ctime(lastTime)` 
| `security_content_ctime(firstTime)` 
| `kerberos_service_ticket_request_using_rc4_encryption_filter`

Macros

The SPL above uses the following Macros:

:information_source: kerberos_service_ticket_request_using_rc4_encryption_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required fields

List of fields required to use this analytic.

  • _time
  • EventCode
  • Ticket_Options
  • Ticket_Encryption_Type
  • dest
  • service
  • service_id

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

Based on Microsoft documentation, legacy systems or applications will use RC4-HMAC as the default encryption for Kerberos Service Ticket requests. Specifically, systems before Windows Server 2008 and Windows Vista. Newer systems will use AES128 or AES256.

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
45.0 90 50 A Kerberos Service TTicket request with RC4 encryption was requested from $dest$

:information_source: The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

Reference

Test Dataset

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

source | version: 3