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About Execution Policies

JuanPablo Jofre|Last Updated: 11/17/2016
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2 Contributors

about_Execution_Policies

SHORT DESCRIPTION

Describes the Windows PowerShell execution policies and explains how to manage them.

LONG DESCRIPTION

Windows PowerShell execution policies let you determine the conditions under which Windows PowerShell loads configuration files and runs scripts.

You can set an execution policy for the local computer, for the current user, or for a particular session. You can also use a Group Policy setting to set execution policy for computers and users.

Execution policies for the local computer and current user are stored in the registry. You do not need to set execution policies in your Windows PowerShell profile. The execution policy for a particular session is stored only in memory and is lost when the session is closed.

The execution policy is not a security system that restricts user actions. For example, users can easily circumvent a policy by typing the script contents at the command line when they cannot run a script. Instead, the execution policy helps users to set basic rules and prevents them from violating them unintentionally.

WINDOWS POWERSHELL EXECUTION POLICIES


The Windows PowerShell execution policies are as follows:

"Restricted" is the default policy.

Restricted

  • Default execution policy in Windows 8, Windows Server 2012, and Windows 8.1.

  • Permits individual commands, but will not run scripts.

  • Prevents running of all script files, including formatting and configuration files (.ps1xml), module script files (.psm1), and Windows PowerShell profiles (.ps1).

AllSigned

  • Scripts can run.

  • Requires that all scripts and configuration files be signed by a trusted publisher, including scripts that you write on the local computer.

  • Prompts you before running scripts from publishers that you have not yet classified as trusted or untrusted.

  • Risks running signed, but malicious, scripts.

RemoteSigned

  • Scripts can run. This is the default execution policy in Windows Server 2012 R2.

  • Requires a digital signature from a trusted publisher on scripts and configuration files that are downloaded from the Internet (including e-mail and instant messaging programs).

  • Does not require digital signatures on scripts that you have written on the local computer (not downloaded from the Internet).

  • Runs scripts that are downloaded from the Internet and not signed, if the scripts are unblocked, such as by using the Unblock-File cmdlet.

  • Risks running unsigned scripts from sources other than the Internet and signed, but malicious, scripts.

Unrestricted

  • Unsigned scripts can run. (This risks running malicious scripts.)

  • Warns the user before running srcipts and configuration files that are downloaded from the Internet.

Bypass

  • Nothing is blocked and there are no warnings or prompts.

  • This execution policy is designed for configurations in which a Windows PowerShell script is built in to a a larger application or for configurations in which Windows PowerShell is the foundation for a program that has its own security model.

Undefined

  • There is no execution policy set in the current scope.

  • If the execution policy in all scopes is Undefined, the effective execution policy is Restricted, which is the default execution policy.

Note: On systems that do not distinguish Universal Naming Convention (UNC) paths from Internet paths, scripts that are identified by a UNC path might not be permitted to run with the RemoteSigned execution policy.

EXECUTION POLICY SCOPE


You can set an execution policy that is effective only in a particular scope.

The valid values for Scope are Process, CurrentUser, and LocalMachine. LocalMachine is the default when setting an execution policy.

The Scope values are listed in precedence order.

  • Process The execution policy affects only the current session (the current Windows PowerShell process).

The execution policy is stored in the $env:PSExecutionPolicyPreference environment variable, not in the registry, and it is deleted when the session is closed. You cannot change the policy by editing the variable value.

  • CurrentUser The execution policy affects only the current user. It is stored in the HKEY_CURRENT_USER registry subkey.

  • LocalMachine The execution policy affects all users on the current computer. It is stored in the HKEY_LOCAL_MACHINE registry subkey.

The policy that takes precedence is effective in the current session, even if a more restrictive policy was set at a lower level of precedence.

For more information, see Set-ExecutionPolicy.

GET YOUR EXECUTION POLICY


To get the Windows PowerShell execution policy that is in effect in the current session, use the Get-ExecutionPolicy cmdlet.

The following command gets the current execution policy:

Get-ExecutionPolicy

To get all of the execution policies that affect the current session and displays them in precedence order, type:

Get-ExecutionPolicy -List

The result will look similar to the following sample output:

Scope ExecutionPolicy


MachinePolicy Undefined UserPolicy Undefined Process Undefined CurrentUser RemoteSigned LocalMachine AllSigned

In this case, the effective execution policy is RemoteSigned because the execution policy for the current user takes precedence over the execution policy set for the local computer.

To get the execution policy set for a particular scope, use the Scope parameter of Get-ExecutionPolicy.

For example, the following command gets the execution policy for the current user scope.

Get-ExecutionPolicy -Scope CurrentUser

CHANGE YOUR EXECUTION POLICY


To change the Windows PowerShell execution policy on your computer, use the Set-ExecutionPolicy cmdlet.

The change is effective immediately; you do not need to restart Windows PowerShell.

If you set the execution policy for the local computer (the default) or the current user, the change is saved in the registry and remains effective until you change it again.

If you set the execution policy for the current process, it is not saved in the registry. It is retained until the current process and any child processes are closed.

Note: In Windows Vista and later versions of Windows, to run commands that change the execution policy for the local computer (the default), start Windows PowerShell with the "Run as administrator" option.

To change your execution policy, type:

Set-ExecutionPolicy -ExecutionPolicy

For example:

Set-ExecutionPolicy -ExecutionPolicy RemoteSigned

To set the execution policy in a particular scope, type:

Set-ExecutionPolicy -ExecutionPolicy -Scope

For example:

Set-ExecutionPolicy RemoteSigned -Scope CurrentUser

A command to change an execution policy can succeed but still not change the effective execution policy.

For example, a command that sets the execution policy for the local computer can succeed but be overridden by the execution policy for the current user.

REMOVE YOUR EXECUTION POLICY


To remove the execution policy for a particular scope, set the value of the value of the execution policy to Undefined.

For example, to remove the execution policy for all the users of the local computer, type:

Set-ExecutionPolicy Undefined

Or, type:

Set-ExecutionPolicy Undefined -scope LocalMachine

If no execution policy is set in any scope, the effective execution policy is Restricted, which is the default.

SET A DIFFERENT EXECUTION POLICY FOR ONE SESSION


You can use the ExecutionPolicy parameter of PowerShell.exe to set an execution policy for a new Windows PowerShell session. The policy affects only the current session and child sessions.

To set the execution policy for a new session, start Windows PowerShell at the command line (such as Cmd.exe or Windows PowerShell), and then use the ExecutionPolicy parameter of PowerShell.exe to set the execution policy.

For example:

PowerShell.exe -ExecutionPolicy AllSigned

The execution policy that you set is not stored in the registry. Instead, it is stored in the $env:PSExecutionPolicyPreference environment variable. The variable is deleted when you close the session in which the policy is set. You cannot change the policy by editing the variable value.

During the session, the execution policy that is set for the session takes precedence over an execution policy that is set in the registry for the local computer or current user. However, it does not take precedence over the execution policy set by using a Group Policy setting (discussed below).

USE GROUP POLICY TO MANAGE EXECUTION POLICY


You can use the "Turn on Script Execution" Group Policy setting to manage the execution policy of computers in your enterprise. The Group Policy setting overrides the execution policies set in Windows PowerShell in all scopes.

The "Turn on Script Execution" policy settings are as follows:

-- If you disable "Turn on Script Execution", scripts do not run. This is equivalent to the "Restricted" execution policy.

-- If you enable "Turn on Script Execution", you can select an execution policy. The Group Policy settings are equivalent to the following execution policy settings.

Group Policy Execution Policy


Allow all scripts. Unrestricted

Allow local scripts RemoteSigned and remote signed scripts.

Allow only signed AllSigned scripts.

-- If "Turn on Script Execution" is not configured, it has no effect. The execution policy set in Windows PowerShell is effective.

The PowerShellExecutionPolicy.adm and PowerShellExecutionPolicy.admx files add the "Turn on Script Execution" policy to the Computer Configuration and User Configuration nodes in Group Policy Editor in the following paths.

For Windows XP and Windows Server 2003: Administrative Templates\Windows Components\Windows PowerShell

For Windows Vista and later versions of Windows: Administrative Templates\Classic Administrative Templates\ Windows Components\Windows PowerShell

Policies set in the Computer Configuration node take precedence over policies set in the User Configuration node.

The PowerShellExecutionPolicy.adm file is available on the Microsoft Download Center. For more information, see "Administrative Templates for Windows PowerShell" at http://go.microsoft.com/fwlink/?LinkId=131786.

For more information, see about_Group_Policy_Settings at http://go.microsoft.com/fwlink/?LinkID=251696.

EXECUTION POLICY PRECEDENCE


When determining the effective execution policy for a session, Windows PowerShell evaluates the execution policies in the following precedence order:

  • Group Policy: Computer Configuration
  • Group Policy: User Configuration
  • Execution Policy: Process (or PowerShell.exe -ExecutionPolicy)
  • Execution Policy: CurrentUser
  • Execution Policy: LocalMachine

MANAGE SIGNED AND UNSIGNED SCRIPTS


If your Windows PowerShell execution policy is RemoteSigned, Windows PowerShell will not run unsigned scripts that are downloaded from the Internet (including e-mail and instant messaging programs).

You can sign the script or elect to run an unsigned script without changing the execution policy.

Beginning in Windows PowerShell 3.0, you can use the Stream parameter of the Get-Item cmdlet to detect files that are blocked because they were downloaded from the Internet, and you can use the Unblock-File cmdlet to unblock the scripts so that you can run them in Windows PowerShell.

For more information, see about_Signing, Get-Item, and Unblock-File.

SEE ALSO

about_Environment_Variables about_Signing Get-ExecutionPolicy Set-ExecutionPolicy Get-Item Unblock-File "Administrative Templates for Windows PowerShell" (http://go.microsoft.com/fwlink/?LinkId=131786) "PowerShell.exe Console Help" (http://go.microsoft.com/fwlink/?LinkID=113439)

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