Potential PowerShell Execution Policy Tampering - ProcCreation

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

Detects changes to the PowerShell execution policy registry key in order to bypass signing requirements for script execution from the CommandLine

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_path`

or:
CommandLine|contains: '\Policies\Microsoft\Windows\PowerShell\ExecutionPolicy'
CommandLine|contains: '\ShellIds\Microsoft.PowerShell\ExecutionPolicy'

Stage 2: `all of selection_values`

or:
CommandLine|contains: Bypass
CommandLine|contains: RemoteSigned
CommandLine|contains: Unrestricted

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	`Bypass` corpus 2 (sigma 2) `RemoteSigned` `Unrestricted` corpus 2 (sigma 2) `\Policies\Microsoft\Windows\PowerShell\ExecutionPolicy` `\ShellIds\Microsoft.PowerShell\ExecutionPolicy`