PSScriptPolicyTest Creation By Uncommon Process

Severity: medium
Author: Nasreddine Bencherchali (Nextron Systems)
Source: upstream

Detects the creation of the "PSScriptPolicyTest" PowerShell script by an uncommon process. This file is usually generated by Microsoft Powershell to test against Applocker.

Event coverage

Provider	Event ID	Title
Sysmon	11	FileCreate

Stages and Predicates

Stage 1: `selection`

TargetFilename|contains: __PSScriptPolicyTest_

Stage 2: `not 1 of filter_main_*`

or:
or:
Image|contains: 'C:\Program Files\WindowsApps\Microsoft.PowerShellPreview'
Image|contains: '\AppData\Local\Microsoft\WindowsApps\Microsoft.PowerShellPreview'
Image|endswith: '\pwsh.exe'
Image: 'C:\Program Files\PowerShell\7-preview\pwsh.exe'
Image: 'C:\Program Files\PowerShell\7\pwsh.exe'
Image: 'C:\Windows\SysWOW64\WindowsPowerShell\v1.0\powershell.exe'
Image: 'C:\Windows\SysWOW64\WindowsPowerShell\v1.0\powershell_ise.exe'
Image: 'C:\Windows\SysWOW64\sdiagnhost.exe'
Image: 'C:\Windows\System32\ServerManager.exe'
Image: 'C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe'
Image: 'C:\Windows\System32\WindowsPowerShell\v1.0\powershell_ise.exe'
Image: 'C:\Windows\System32\dsac.exe'
Image: 'C:\Windows\System32\sdiagnhost.exe'
Image: 'C:\Windows\System32\wsmprovhost.exe'

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

Field	Kind	Values
`Image`	ends_with	`\pwsh.exe` corpus 140 (sigma 140)
`Image`	eq	`C:\Program Files\PowerShell\7-preview\pwsh.exe` corpus 3 (sigma 3) `C:\Program Files\PowerShell\7\pwsh.exe` corpus 4 (sigma 4) `C:\Windows\SysWOW64\WindowsPowerShell\v1.0\powershell.exe` corpus 3 (sigma 3) `C:\Windows\SysWOW64\WindowsPowerShell\v1.0\powershell_ise.exe` corpus 2 (sigma 2) `C:\Windows\SysWOW64\sdiagnhost.exe` `C:\Windows\System32\ServerManager.exe` corpus 3 (sigma 3) `C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe` corpus 4 (sigma 4) `C:\Windows\System32\WindowsPowerShell\v1.0\powershell_ise.exe` corpus 3 (sigma 3) `C:\Windows\System32\dsac.exe` corpus 2 (sigma 2) `C:\Windows\System32\sdiagnhost.exe` corpus 2 (sigma 2) `C:\Windows\System32\wsmprovhost.exe` corpus 2 (sigma 2)
`Image`	match	`C:\Program Files\WindowsApps\Microsoft.PowerShellPreview` corpus 4 (sigma 4) `\AppData\Local\Microsoft\WindowsApps\Microsoft.PowerShellPreview` corpus 4 (sigma 4)
`TargetFilename`	match	`__PSScriptPolicyTest_` corpus 2 (sigma 2)