Detection: Kerberos Pre-Authentication Flag Disabled in UserAccountControl

Updated Date: 2024-09-30 ID: 0cb847ee-9423-11ec-b2df-acde48001122 Author: Mauricio Velazco, Splunk Type: TTP Product: Splunk Enterprise Security

Description

The following analytic detects when the Kerberos Pre-Authentication flag is disabled in a user account, using Windows Security Event 4738. This event indicates a change in the UserAccountControl property of a domain user object. Disabling this flag allows adversaries to perform offline brute force attacks on the user's password using the AS-REP Roasting technique. This activity is significant as it can be used by attackers with existing privileges to escalate their access or maintain persistence. If confirmed malicious, this could lead to unauthorized access and potential compromise of sensitive information.

1`wineventlog_security` EventCode=4738 MSADChangedAttributes="*Don't Require Preauth' - Enabled*" 
2|rename Account_Name as user 
3| table EventCode, user, dest, Security_ID, MSADChangedAttributes 
4| `kerberos_pre_authentication_flag_disabled_in_useraccountcontrol_filter`

Data Source

Name Platform Sourcetype Source
Windows Event Log Security 4738 Windows icon Windows 'xmlwineventlog' 'XmlWinEventLog:Security'

Macros Used

Name Value
wineventlog_security eventtype=wineventlog_security OR Channel=security OR source=XmlWinEventLog:Security
kerberos_pre_authentication_flag_disabled_in_useraccountcontrol_filter search *
kerberos_pre_authentication_flag_disabled_in_useraccountcontrol_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 search, you need to be ingesting Domain Controller events. The Advanced Security Audit policy setting User Account Management within Account Management needs to be enabled.

Known False Positives

Unknown.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message Risk Score Impact Confidence
Kerberos Pre Authentication was Disabled for $user$ 45 50 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 WinEventLog:Security WinEventLog
Integration ✅ Passing Dataset WinEventLog:Security WinEventLog

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: 4