Suspicious Kerberos Service Ticket Request

Try in Splunk Security Cloud

Description

The following analytic detects suspicious Kerberos Service Ticket (TGS) requests where the requesting account name matches the service name, potentially indicating an exploitation attempt of CVE-2021-42278 and CVE-2021-42287. This detection leverages Event ID 4769 from Domain Controller and Kerberos events. Such activity is significant as it may represent an adversary attempting to escalate privileges by impersonating a domain controller. If confirmed malicious, this could allow an attacker to take control of the domain controller, leading to complete domain compromise and unauthorized access to sensitive information.

• Type: TTP

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

• Last Updated: 2024-05-16
• Author: Mauricio Velazco, Splunk
• ID: 8b1297bc-6204-11ec-b7c4-acde48001122

Annotations

ATT&CK

ATT&CK

ID	Technique	Tactic
T1078	Valid Accounts	Defense Evasion, Persistence, Privilege Escalation, Initial Access

T1078.002

Domain Accounts

Defense Evasion, Persistence, Privilege Escalation, Initial Access

Kill Chain Phase

• Exploitation
• Installation
• Delivery

NIST

• DE.CM

CIS20

• CIS 10

CVE

Search

 `wineventlog_security` EventCode=4769 
| eval isSuspicious = if(lower(ServiceName) = lower(mvindex(split(TargetUserName,"@"),0)),1,0) 
| where isSuspicious = 1 
| rename Computer as dest
| rename TargetUserName as user 
| table _time, dest, src_ip, user, ServiceName, Error_Code, isSuspicious 
| `suspicious_kerberos_service_ticket_request_filter`

Macros

The SPL above uses the following Macros:

• wineventlog_security

suspicious_kerberos_service_ticket_request_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
• Service_Name
• Account_Name
• Client_Address
• Failure_Code

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

We have tested this detection logic with ~2 million 4769 events and did not identify false positives. However, they may be possible in certain environments. Filter as needed.

Associated Analytic Story

• sAMAccountName Spoofing and Domain Controller Impersonation
• Active Directory Kerberos Attacks
• Active Directory Privilege Escalation

RBA

Risk Score	Impact	Confidence	Message
60.0	100	60	A suspicious Kerberos Service Ticket was requested by $user$ on host $dest$

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

• https://exploit.ph/cve-2021-42287-cve-2021-42278-weaponisation.html
• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-42278
• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-42287
• https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-sfu/02636893-7a1f-4357-af9a-b672e3e3de13

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