The name of an account was changed
A user account or computer account (`sAMAccountName`) was renamed.
Event ID 4781 logs account renaming (`OldTargetUserName` changed to `NewTargetUserName`). While legitimate for user name changes, adversaries frequently rename the built-in `Administrator` account or guest account to blend in with normal service account naming conventions (`sAMAccountName spoofing`).
Failure Reason / Root Cause:
Account rename operation (`OldTargetUserName` renamed to `NewTargetUserName`).
Raw Event XML snippet
<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
<System>
<Provider Name="Microsoft-Windows-Security-Auditing" Guid="{54849625-5478-4994-A5BA-3E3B0328C30D}" />
<EventID>4781</EventID>
<Version>0</Version>
<Level>0</Level>
<Task>12544</Task>
<Opcode>0</Opcode>
<Keywords>0x8020000000000000</Keywords>
<TimeCreated SystemTime="2026-07-17T09:54:44.912Z" />
<EventRecordID>1048576</EventRecordID>
<Correlation />
<Execution ProcessID="612" ThreadID="1024" />
<Channel>Security</Channel>
<Computer>DC01.enterprise.internal</Computer>
<Security />
</System>
<EventData>
<Data Name="SubjectUserSid">S-1-5-18</Data>
<Data Name="SubjectUserName">SYSTEM</Data>
<Data Name="SubjectDomainName">NT AUTHORITY</Data>
<Data Name="SubjectLogonId">0x3e7</Data>
<!-- Event telemetry fields specific to The name of an account was changed -->
</EventData>
</Event>MITRE ATT&CK mapping
| ID | Technique | Tactic |
|---|---|---|
T1036 | Masquerading: Rename System Utilities / Accounts | Defense Evasion |
T1098 | Account Manipulation | Persistence |
Recommended actions
- Inspect `TargetSid` and `OldTargetUserName`. If the built-in Administrator account (`SID S-1-5-21...-500`) is renamed to an innocuous name, or if a guest account (`-501`) is renamed and enabled, alert immediately.