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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.

  • Type: TTP
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Change
  • Last Updated: 2024-05-24
  • Author: Mauricio Velazco, Splunk
  • ID: 0cb847ee-9423-11ec-b2df-acde48001122

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1558 Steal or Forge Kerberos Tickets Credential Access
T1558.004 AS-REP Roasting Credential Access
Kill Chain Phase
  • Exploitation
NIST
  • DE.CM
CIS20
  • CIS 10
CVE 


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

Macros

The SPL above uses the following Macros:

:information_source: kerberos_pre-authentication_flag_disabled_in_useraccountcontrol_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
  • Account_Name
  • Security_ID
  • MSADChangedAttributes

How To Implement

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

RBA

Risk Score Impact Confidence Message
45.0 50 90 Kerberos Pre Authentication was Disabled for $user$

: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: 2