Execute Code with Pester.bat as Parent

Severity: medium
Author: frack113, Nasreddine Bencherchali
Source: upstream

Detects code execution via Pester.bat (Pester - Powershell Modulte for testing)

MITRE ATT&CK coverage

Tactic	Techniques
Execution	`T1059.001` Command and Scripting Interpreter: PowerShell
Defense Evasion	`T1216` System Script Proxy Execution

Event coverage

Provider	Event ID	Title
Sysmon	1	Process creation

Stages and Predicates

Stage 1: `all of selection_module`

or:
ParentImage|endswith: '\powershell.exe'
ParentImage|endswith: '\pwsh.exe'
ParentCommandLine|contains: '\WindowsPowerShell\Modules\Pester\'

Stage 2: `all of selection_cli`

or:
ParentCommandLine|contains: '{ Get-Help "'
ParentCommandLine|contains: '{ Invoke-Pester -EnableExit ;'

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
`ParentCommandLine`	match	`\WindowsPowerShell\Modules\Pester\` `{ Get-Help "` `{ Invoke-Pester -EnableExit ;`
`ParentImage`	ends_with	`\powershell.exe` corpus 16 (sigma 16) `\pwsh.exe` corpus 16 (sigma 16)