Detection: Disabled Kerberos Pre-Authentication Discovery With Get-ADUser

Updated Date: 2024-09-30 ID: 114c6bfe-9406-11ec-bcce-acde48001122 Author: Mauricio Velazco, Splunk Type: TTP Product: Splunk Enterprise Security

Description

The following analytic detects the execution of the Get-ADUser PowerShell cmdlet with parameters indicating a search for domain accounts with Kerberos Pre-Authentication disabled. It leverages PowerShell Script Block Logging (EventCode=4104) to identify this specific activity. This behavior is significant because discovering accounts with Kerberos Pre-Authentication disabled can allow adversaries to perform offline password cracking. If confirmed malicious, this activity could lead to unauthorized access to user accounts, potentially compromising sensitive information and escalating privileges within the network.

1`powershell` EventCode=4104 (ScriptBlockText = "*Get-ADUser*" AND ScriptBlockText="*4194304*") 
2| stats count min(_time)  as firstTime max(_time) as lastTime by Opcode Computer UserID EventCode ScriptBlockText 
3| rename Computer as dest 
4| `security_content_ctime(firstTime)` 
5| `disabled_kerberos_pre_authentication_discovery_with_get_aduser_filter`

Data Source

Name Platform Sourcetype Source
Powershell Script Block Logging 4104 Windows icon Windows 'xmlwineventlog' 'XmlWinEventLog:Microsoft-Windows-PowerShell/Operational'

Macros Used

Name Value
powershell (source=WinEventLog:Microsoft-Windows-PowerShell/Operational OR source="XmlWinEventLog:Microsoft-Windows-PowerShell/Operational")
disabled_kerberos_pre_authentication_discovery_with_get_aduser_filter search *
disabled_kerberos_pre_authentication_discovery_with_get_aduser_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
T1558 Steal or Forge Kerberos Tickets Credential Access
T1558.004 AS-REP Roasting Credential Access
KillChainPhase.EXPLOITAITON
NistCategory.DE_CM
Cis18Value.CIS_10

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 Notable Yes
Rule Title %name%
Rule Description %description%
Notable Event Fields user, dest
Creates Risk Event True
This configuration file applies to all detections of type TTP. These detections will use Risk Based Alerting and generate Notable Events.

Implementation

To successfully implement this analytic, you will need to enable PowerShell Script Block Logging on some or all endpoints. Additional setup here https://docs.splunk.com/Documentation/UBA/5.0.4.1/GetDataIn/AddPowerShell#Configure_module_logging_for_PowerShell.

Known False Positives

Administrators or power users may use search for accounts with Kerberos Pre Authentication disabled for legitimate purposes.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message Risk Score Impact Confidence
Disabled Kerberos Pre-Authentication Discovery With Get-ADUser from $dest$ 54 60 90
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:Microsoft-Windows-PowerShell/Operational XmlWinEventLog
Integration ✅ Passing Dataset XmlWinEventLog:Microsoft-Windows-PowerShell/Operational 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: 5