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Description

As part of the sAMAccountName Spoofing (CVE-2021-42278) and Domain Controller Impersonation (CVE-2021-42287) exploitation chain, adversaries need to create a new computer account name and rename it to match the name of a domain controller account without the ending '$'. In Windows Active Directory environments, computer account names always end with $. This analytic leverages Event Id 4781, The name of an account was changed, to identify a computer account rename event with a suspicious name that does not terminate with $. This behavior could represent an exploitation attempt of CVE-2021-42278 and CVE-2021-42287 for privilege escalation.

  • Type: TTP

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

  • Last Updated: 2021-12-20
  • Author: Mauricio Velazco, Splunk
  • ID: 35a61ed8-61c4-11ec-bc1e-acde48001122

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1078 Valid Accounts Defense Evasion, Persistence, Privilege Escalation, Initial Access
T1078.002 Domain Accounts Defense Evasion, Persistence, Privilege Escalation, Initial Access
Kill Chain Phase
  • Exploitation
  • Installation
  • Delivery
NIST
  • DE.CM
CIS20
  • CIS 10
CVE
ID Summary CVSS
CVE-2021-42287 Active Directory Domain Services Elevation of Privilege Vulnerability This CVE ID is unique from CVE-2021-42278, CVE-2021-42282, CVE-2021-42291. 6.5
CVE-2021-42278 Active Directory Domain Services Elevation of Privilege Vulnerability This CVE ID is unique from CVE-2021-42282, CVE-2021-42287, CVE-2021-42291. 6.5 


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`wineventlog_security` EventCode=4781 Old_Account_Name="*$" New_Account_Name!="*$" 
| table _time, ComputerName, Account_Name, Old_Account_Name, New_Account_Name 
| `suspicious_computer_account_name_change_filter`

Macros

The SPL above uses the following Macros:

:information_source: suspicious_computer_account_name_change_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
  • ComputerName
  • Account_Name
  • Old_Account_Name
  • New_Account_Name

How To Implement

To successfully implement this search, you need to be ingesting Windows event logs from your hosts. In addition, the Splunk Windows TA is needed.

Known False Positives

Renaming a computer account name to a name that not end with '$' is highly unsual and may not have any legitimate scenarios.

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
70.0 100 70 A computer account $Old_Account_Name$ was renamed with a suspicious computer name

: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

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