AppLocker

This article provides a description of AppLocker and can help you decide if your organization can benefit from deploying AppLocker policies. AppLocker helps you control which apps and files users can run. These include executable files, scripts, Windows Installer files, dynamic-link libraries (DLLs), packaged apps, and packaged app installers. AppLocker is also used by some features of App Control for Business.

AppLocker can help you:

• Define rules based on file attributes that persist across app updates, such as the publisher name (derived from the digital signature), product name, file name, and file version. You can also create rules based on the file path and hash.
• Assign a rule to a security group or an individual user.
• Create exceptions to rules. For example, you can create a rule that allows all users to run all Windows binaries, except the Registry Editor (regedit.exe).
• Use audit-only mode to deploy the policy and understand its effect before enforcing it.
• Create rules on a staging server, test them, then export them to your production environment and import them into a Group Policy Object.
• Create and manage AppLocker rules by using Windows PowerShell.

AppLocker helps prevent users from running unapproved apps. AppLocker addresses the following app control scenarios:

• Application inventory: AppLocker has the ability to apply its policy in an audit-only mode where all app launch activity is allowed but registered in event logs. These events can be collected for further analysis. Windows PowerShell cmdlets also help you analyze this data programmatically.
• Protection against unwanted software: AppLocker has the ability to deny apps from running when you exclude them from the list of allowed apps. When AppLocker rules are enforced in the production environment, any apps that aren't included in the allowed rules are blocked from running.
• Licensing conformance: AppLocker can help you create rules that preclude unlicensed software from running and restrict licensed software to authorized users.
• Software standardization: AppLocker policies can be configured to allow only supported or approved apps to run on computers within a business group. This configuration permits a more uniform app deployment.

When to use AppLocker

In many organizations, information is the most valuable asset, and ensuring that only approved users have access to that information is imperative. Access control technologies, such as Active Directory Rights Management Services (AD RMS) and access control lists (ACLs), help control what users are allowed to access.

However, when a user runs a process, that process has the same level of access to data that the user has. As a result, sensitive information could easily be deleted or transmitted out of the organization if a user runs unauthorized software, including malware. AppLocker helps mitigate these types of security issues by restricting the files that users or groups are allowed to run. Because AppLocker can control DLLs and scripts, it's also useful to control who can install and run ActiveX controls.

AppLocker is ideal for organizations that currently use Group Policy to manage their PCs.

The following are examples of scenarios in which AppLocker can be used:

• Your organization's security policy dictates the use of only licensed software, so you need to prevent users from running unlicensed software and also restrict the use of licensed software to authorized users.
• An app is no longer supported by your organization, so you need to prevent it from being used by everyone.
• The potential that unwanted software can be introduced in your environment is high, so you need to reduce this threat.
• The license to an app is revoked or expired in your organization, so you need to prevent it from being used by everyone.
• A new app or a new version of an app is deployed, and you need to prevent users from running the old version.
• Specific software tools aren't allowed within the organization, or only specific users should have access to those tools.
• A single user or small group of users needs to use a specific app that is denied for all others.
• Some people in your organization who require different software share a computer, and you need to protect specific apps.
• In addition to other measures, you need to control the access to sensitive data through app usage.

AppLocker can help you protect the digital assets within your organization, reduce the threat of malicious software being introduced into your environment, and improve the management of application control and the maintenance of application control policies.

Installing AppLocker

AppLocker is included with all editions of Windows except Windows 10 version 1809 or earlier. You can author AppLocker rules for a single computer or for a group of computers. For a single computer, you can author the rules by using the Local Security Policy editor (secpol.msc). For a group of computers, you can author the rules within a Group Policy Object by using the Group Policy Management Console (GPMC).

Using AppLocker on Server Core

AppLocker on Server Core installations isn't supported.

Virtualization considerations

You can administer AppLocker policies by using a virtualized instance of Windows provided it meets all the system requirements listed previously. You can also run Group Policy in a virtualized instance. However, you risk losing the policies that you create and maintain if the virtualized instance is removed or fails.

Security considerations

Application control policies specify which apps are allowed to run on the local computer. The variety of forms that malicious software can take make it difficult for users to know what is safe to run. When activated, malicious software can damage content on a hard disk drive, flood a network with requests to cause a denial-of-service (DoS) attack, send confidential information to the Internet, or compromise the security of a computer.

The countermeasure is to create a sound design for your application control policies on PCs in your organization. AppLocker can be part of your app control strategy because you can control what software is allowed to run on your computers.

A flawed application control policy implementation can disable necessary applications or allow malicious or unintended software to run. You should thoroughly test the policies in a lab environment before you deploy them in production. It's also important that organizations dedicate sufficient resources to manage and troubleshoot the implementation of such policies.

For more information about specific security issues, see Security considerations for AppLocker. When you use AppLocker to create application control policies, you should be aware of the following security considerations:

• Who has the rights to set AppLocker policies?
• How do you validate that the policies are enforced?
• What events should you audit?

For reference in your security planning, the following table identifies the baseline settings for a PC with AppLocker installed:

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