Detection: Suspicious Computer Account Name Change

Updated Date: 2025-02-10 ID: 35a61ed8-61c4-11ec-bc1e-acde48001122 Author: Mauricio Velazco, Splunk Type: TTP Product: Splunk Enterprise Security

Description

The following analytic detects a suspicious computer account name change in Active Directory. It leverages Event ID 4781, which logs account name changes, to identify instances where a computer account name is changed to one that does not end with a $. This behavior is significant as it may indicate an attempt to exploit CVE-2021-42278 and CVE-2021-42287, which can lead to domain controller impersonation and privilege escalation. If confirmed malicious, this activity could allow an attacker to gain elevated privileges and potentially control the domain.

Search

1`wineventlog_security` EventCode=4781 OldTargetUserName="*$" NewTargetUserName!="*$" 
2| table _time, Computer, Caller_User_Name, OldTargetUserName, NewTargetUserName 
3| rename Computer as dest 
4| `suspicious_computer_account_name_change_filter`

Data Source

Name	Platform	Sourcetype	Source
Windows Event Log Security 4781	Windows	`'xmlwineventlog'`	`'XmlWinEventLog:Security'`

Macros Used

Name	Value
wineventlog_security	`eventtype="wineventlog_security" OR Channel="security" OR source="XmlWinEventLog:Security" OR source="WinEventLog:Security"`
suspicious_computer_account_name_change_filter	`search *`

suspicious_computer_account_name_change_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
T1078.002	Domain Accounts	Defense Evasion

Delivery

Exploitation

Installation

DE.CM

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 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

Risk Based Analytics (RBA)

Risk Message:

A computer account $OldTargetUserName$ was renamed with a suspicious computer name on $dest$

Risk Object	Risk Object Type	Risk Score	Threat Objects
OldTargetUserName	user	70	No Threat Objects
dest	system	70	No Threat Objects

References

Detection Testing

Test Type	Status	Dataset	Source	Sourcetype
Validation	✅ Passing	N/A	N/A	N/A
Unit	✅ Passing	Dataset	`XmlWinEventLog:Security`	`XmlWinEventLog`
Integration	✅ Passing	Dataset	`XmlWinEventLog:Security`	`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: 8