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Description

The following analytic leverages Windows Security Event 4738, A user account was changed, to identify a change performed on a domain user object that disables Kerberos Pre-Authentication. Disabling the Pre Authentication flag in the UserAccountControl property allows an adversary to easily perform a brute force attack against the user’s password offline leveraging the ASP REP Roasting technique. Red Teams and adversaries alike who have obtained privileges in an Active Directory network may use this technique as a backdoor or a way to escalate privileges.

  • Type: TTP

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

  • Last Updated: 2022-02-22
  • Author: Mauricio Velazco, Splunk
  • ID: 0cb847ee-9423-11ec-b2df-acde48001122

Annotations

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
CIS20
CVE 
1
2
3

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

Macros

The SPL above uses the following Macros:

Note that 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 field

  • _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 $Account_Name$

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: 1