Engine state is changed from None to Available
The PowerShell host engine (`powershell.exe` or runspace host) initialized and started execution.
Event ID 400 (`Windows PowerShell` / `Operational`) records the initialization and startup of the PowerShell engine (`HostName`, `HostVersion`, `HostApplication`). When threat actors execute PowerShell via custom runspaces inside non-standard applications (`System.Management.Automation` hosted in `msbuild.exe` or `rundll32.exe`), event `400` reveals the anomalous `HostApplication` path.
Failure Reason / Root Cause:
PowerShell runspace engine initialization (`HostApplication` command line shown).
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>400</EventID>
<Version>0</Version>
<Level>0</Level>
<Task>12544</Task>
<Opcode>0</Opcode>
<Keywords>0x8020000000000000</Keywords>
<TimeCreated SystemTime="2026-07-17T09:54:44.846Z" />
<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 Engine state is changed from None to Available -->
</EventData>
</Event>MITRE ATT&CK mapping
| ID | Technique | Tactic |
|---|---|---|
T1059.001 | Command and Scripting Interpreter: PowerShell | Execution |
T1218 | System Binary Proxy Execution | Defense Evasion |
Recommended actions
- Inspect `HostApplication`. Alert immediately if the PowerShell engine starts inside processes other than `powershell.exe`, `pwsh.exe`, `wsmprovhost.exe`, or standard management tools (`Unmanaged PowerShell runspace injection`).