Suspicious WindowsTerminal Child Processes

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

Detects suspicious children spawned via the Windows Terminal application which could be a sign of persistence via WindowsTerminal (see references section)

Event coverage

Provider	Event ID	Title
Sysmon	1	Process creation
Security-Auditing	4688	A new process has been created.

Stages and Predicates

Stage 1: `all of selection_parent`

or:
ParentImage|endswith: '\WindowsTerminal.exe'
ParentImage|endswith: '\wt.exe'

Stage 2: `all of selection_susp`

or:
CommandLine|contains: ' /c '
CommandLine|contains: ' /k '
CommandLine|contains: ' /r '
CommandLine|contains: ' icm'
CommandLine|contains: ' iex '
CommandLine|contains: 'DownloadString('
CommandLine|contains: 'Import-Module '
CommandLine|contains: Invoke-
CommandLine|contains: 'ipmo '
Image|endswith: '\certutil.exe'
Image|endswith: '\csc.exe'
Image|endswith: '\cscript.exe'
Image|endswith: '\regsvr32.exe'
Image|endswith: '\rundll32.exe'
Image|endswith: '\wscript.exe'
Image|contains: 'C:\Users\Public\'
Image|contains: '\AppData\Local\Temp\'
Image|contains: '\Desktop\'
Image|contains: '\Downloads\'
Image|contains: '\Windows\TEMP\'

Stage 3: `not 1 of filter_*`

or:
CommandLine|contains: 'C:\Program Files\Microsoft Visual Studio\'
CommandLine|contains: '\Common7\Tools\VsDevCmd.bat'
CommandLine|contains: Enter-VsDevShell
CommandLine|contains: Import-Module
CommandLine|contains: 'Microsoft.VisualStudio.DevShell.dll'
CommandLine|contains: '\AppData\Local\Packages\Microsoft.WindowsTerminal_'
CommandLine|contains: '\LocalState\settings.json'

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
`CommandLine`	match	`/c` corpus 2 (sigma 2) `/k` `/r` `icm` `iex` `C:\Program Files\Microsoft Visual Studio\` `DownloadString(` `Enter-VsDevShell` `Import-Module` `Import-Module` corpus 2 (sigma 2) `Invoke-` corpus 5 (sigma 5) `Microsoft.VisualStudio.DevShell.dll` `\AppData\Local\Packages\Microsoft.WindowsTerminal_` `\Common7\Tools\VsDevCmd.bat` `\LocalState\settings.json` `ipmo` corpus 2 (sigma 2)
`Image`	ends_with	`\certutil.exe` corpus 34 (sigma 34) `\csc.exe` corpus 5 (sigma 5) `\cscript.exe` corpus 64 (sigma 64) `\regsvr32.exe` corpus 57 (sigma 57) `\rundll32.exe` corpus 76 (sigma 76) `\wscript.exe` corpus 64 (sigma 64)
`Image`	match	`C:\Users\Public\` corpus 2 (sigma 2) `\AppData\Local\Temp\` corpus 9 (sigma 9) `\Desktop\` corpus 6 (sigma 6) `\Downloads\` corpus 8 (sigma 8) `\Windows\TEMP\`
`ParentImage`	ends_with	`\WindowsTerminal.exe` corpus 3 (sigma 3) `\wt.exe`