Potential Binary Or Script Dropper Via PowerShell

Severity: medium
Author: frack113, Nasreddine Bencherchali (Nextron Systems)
Source: upstream

Detects PowerShell creating a binary executable or a script file.

Event coverage

Provider	Event ID	Title
Sysmon	11	FileCreate

Stages and Predicates

Stage 1: `selection`

or:
Image|endswith: '\powershell.exe'
Image|endswith: '\powershell_ise.exe'
Image|endswith: '\pwsh.exe'
or:
TargetFilename|endswith: .bat
TargetFilename|endswith: .chm
TargetFilename|endswith: .cmd
TargetFilename|endswith: .com
TargetFilename|endswith: .dll
TargetFilename|endswith: .exe
TargetFilename|endswith: .hta
TargetFilename|endswith: .jar
TargetFilename|endswith: .js
TargetFilename|endswith: .ocx
TargetFilename|endswith: .scr
TargetFilename|endswith: .sys
TargetFilename|endswith: .vbe
TargetFilename|endswith: .vbs
TargetFilename|endswith: .wsf

Stage 2: `not 1 of filter_main_*`

or:
or:
TargetFilename|endswith: .dll
TargetFilename|endswith: .exe
or:
TargetFilename|startswith: 'C:\Windows\SystemTemp\'
TargetFilename|startswith: 'C:\Windows\Temp\'
or:
TargetFilename|endswith: .dll
TargetFilename|endswith: .exe
TargetFilename|contains: '\AppData\Local\Temp\'
TargetFilename|startswith: 'C:\Users\'
TargetFilename|endswith: .dll
TargetFilename|contains: '\WindowsPowerShell\Modules\'
TargetFilename|startswith: 'C:\Users\'
TargetFilename|endswith: '\Microsoft.PackageManagement.NuGetProvider.dll'
TargetFilename|startswith: 'C:\Program Files\PackageManagement\ProviderAssemblies\nuget\'

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	`\powershell.exe` corpus 143 (sigma 143) `\powershell_ise.exe` corpus 27 (sigma 27) `\pwsh.exe` corpus 140 (sigma 140)
`TargetFilename`	ends_with	`.bat` corpus 15 (sigma 15) `.chm` corpus 3 (sigma 3) `.cmd` corpus 8 (sigma 8) `.com` corpus 3 (sigma 3) `.dll` corpus 21 (sigma 21) `.exe` corpus 18 (sigma 18) `.hta` corpus 12 (sigma 12) `.jar` corpus 2 (sigma 2) `.js` corpus 8 (sigma 8) `.ocx` corpus 3 (sigma 3) `.scr` corpus 8 (sigma 8) `.sys` corpus 6 (sigma 6) `.vbe` corpus 13 (sigma 13) `.vbs` corpus 16 (sigma 16) `.wsf` corpus 6 (sigma 6) `\Microsoft.PackageManagement.NuGetProvider.dll`
`TargetFilename`	match	`\AppData\Local\Temp\` corpus 11 (sigma 11) `\WindowsPowerShell\Modules\` corpus 3 (sigma 3)
`TargetFilename`	starts_with	`C:\Program Files\PackageManagement\ProviderAssemblies\nuget\` `C:\Users\` corpus 12 (sigma 12) `C:\Windows\SystemTemp\` `C:\Windows\Temp\` corpus 4 (sigma 4)