Detection: Suspicious Ticket Granting Ticket Request

Updated Date: 2024-05-25 ID: d77d349e-6269-11ec-9cfe-acde48001122 Author: Mauricio Velazco, Splunk Type: Hunting Product: Splunk Enterprise Security

Description

The following analytic detects suspicious Kerberos Ticket Granting Ticket (TGT) requests that may indicate exploitation of CVE-2021-42278 and CVE-2021-42287. It leverages Event ID 4781 (account name change) and Event ID 4768 (TGT request) to identify sequences where a newly renamed computer account requests a TGT. This behavior is significant as it could represent an attempt to escalate privileges by impersonating a Domain Controller. If confirmed malicious, this activity could allow attackers to gain elevated access and potentially control over the domain environment.

1 `wineventlog_security` (EventCode=4781 OldTargetUserName="*$" NewTargetUserName!="*$") OR (EventCode=4768 TargetUserName!="*$") 
2| eval RenamedComputerAccount = coalesce(NewTargetUserName, TargetUserName) 
3| transaction RenamedComputerAccount startswith=(EventCode=4781) endswith=(EventCode=4768) 
4| eval short_lived=case((duration<2),"TRUE") 
5| search short_lived = TRUE 
6| table _time, Computer, EventCode, TargetUserName, RenamedComputerAccount, short_lived 
7| rename Computer as dest 
8| `suspicious_ticket_granting_ticket_request_filter`

Data Source

Name Platform Sourcetype Source Supported App
Windows Event Log Security 4768 Windows icon Windows 'xmlwineventlog' 'XmlWinEventLog:Security' N/A

Macros Used

Name Value
wineventlog_security eventtype=wineventlog_security OR Channel=security OR source=XmlWinEventLog:Security
suspicious_ticket_granting_ticket_request_filter search *
suspicious_ticket_granting_ticket_request_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Annotations

- MITRE ATT&CK
+ Kill Chain Phases
+ NIST
+ CIS
- Threat Actors
ID Technique Tactic
T1078 Valid Accounts Defense Evasion
T1078.002 Domain Accounts Initial Access
KillChainPhase.DELIVERY
KillChainPhase.EXPLOITAITON
KillChainPhase.INSTALLATION
NistCategory.DE_AE
Cis18Value.CIS_10
APT18
APT28
APT29
APT33
APT39
APT41
Akira
Axiom
Carbanak
Chimera
Cinnamon Tempest
Dragonfly
FIN10
FIN4
FIN5
FIN6
FIN7
FIN8
Fox Kitten
GALLIUM
Ke3chang
LAPSUS$
Lazarus Group
Leviathan
OilRig
POLONIUM
PittyTiger
Sandworm Team
Silence
Silent Librarian
Suckfly
Threat Group-3390
Wizard Spider
menuPass
APT3
APT5
Chimera
Cinnamon Tempest
Indrik Spider
Magic Hound
Naikon
Sandworm Team
TA505
Threat Group-1314
ToddyCat
Volt Typhoon
Wizard Spider

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

Setting Value
Disabled true
Cron Schedule 0 * * * *
Earliest Time -70m@m
Latest Time -10m@m
Schedule Window auto
Creates Risk Event False
This configuration file applies to all detections of type hunting.

Implementation

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

A computer account name change event inmediately followed by a kerberos TGT request with matching fields is unsual. However, legitimate behavior may trigger it. Filter as needed.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message Risk Score Impact Confidence
A suspicious TGT was requested was requested by $dest$ 60 100 60
The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

References

Detection Testing

Test Type Status Dataset Source Sourcetype
Validation ✅ Passing N/A N/A N/A
Unit ✅ Passing Dataset XmlWinEventLog:Security XmlWinEventLog
Integration ✅ Passing Dataset XmlWinEventLog:Security XmlWinEventLog

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: GitHub | Version: 3