Detections
Analytics

2.2.20 Ensure 'Impersonate a client after authentication' is set to 'Administrators, LOCAL SERVICE, NETWORK SERVICE, SERVICE'

Information

The policy setting allows programs that run on behalf of a user to impersonate that user (or another specified account) so that they can act on behalf of the user. If this user right is required for this kind of impersonation, an unauthorized user will not be able to convince a client to connect-for example, by remote procedure call (RPC) or named pipes-to a service that they have created to impersonate that client, which could elevate the unauthorized user's permissions to administrative or system levels.

Services that are started by the Service Control Manager have the built-in Service group added by default to their access tokens. COM servers that are started by the COM infrastructure and configured to run under a specific account also have the Service group added to their access tokens. As a result, these processes are assigned this user right when they are started.

Also, a user can impersonate an access token if any of the following conditions exist:

The access token that is being impersonated is for this user.

The user, in this logon session, logged on to the network with explicit credentials to create the access token.

The requested level is less than Impersonate, such as Anonymous or Identify.

An attacker with the Impersonate a client after authentication user right could create a service, trick a client to make them connect to the service, and then impersonate that client to elevate the attacker's level of access to that of the client.

The recommended state for this setting is: Administrators, LOCAL SERVICE, NETWORK SERVICE, SERVICE.

Note: This user right is considered a 'sensitive privilege' for the purposes of auditing.

Rationale:

An attacker with the Impersonate a client after authentication user right could create a service, trick a client to make them connect to the service, and then impersonate that client to elevate the attacker's level of access to that of the client.

Impact:

In most cases this configuration will have no impact. If you have installed Web Server (IIS), you will need to also assign the user right to IIS_IUSRS.

Solution

To establish the recommended configuration, set the following Device Configuration Policy to Administrators, LOCAL SERVICE, NETWORK SERVICE, SERVICE:

To access the Device Configuration Policy from the Intune Home page:

Click Devices

Click Configuration profiles

Click Create profile

Select the platform (Windows 10 and later)

Select the profile (Endpoint protection)

Click Create

Enter a Name

Click Next

Configure the following Setting

Path: Endpoint protection/User Rights
Setting Name: Impersonate a client
Configuration: Allow and sub-option: Administrators, LOCAL SERVICE, NETWORK SERVICE, SERVICE

Select OK

Continue through the Wizard to complete the creation of the profile (profile assignments, applicability etc.)

Note: More than one configuration setting from each of the Configuration profiles (ex: Administrative Templates, Custom etc.) can be added to each Device Configuration Policy.

Note #2: This setting can also be created via a Custom Configuration Profile using the following OMA-URI:

Name: <Enter name>
Description: <Enter Description>
OMA-URI: ./Device/Vendor/MSFT/Policy/Config/UserRights/ImpersonateClient
Data type: String
Value: Administrators, LOCAL SERVICE, NETWORK SERVICE, SERVICE

Important: When there is more than one value that needs to be entered (ex: Guests, Administrator), the XML value of &#61440; will need to be converted to its Unicode character representation to separate the values in the Value field of the Custom Device Configuration Policy. This value should convert to a square with a question mark in it (). Please note that when copied from the converter to Intune a square will appear, but the value will still work. Also note that this value cannot be copied from sources like Microsoft Word. We recommend that the value be copied and used directly from the converter. A sample converter can be found at Online XML entity decoder | Coder's Toolbox.

Select OK

Continue through the Wizard to complete the creation of the profile (profile assignments, applicability etc.)

Note #3: The following link is an alternative way to set the 'User Rights Assignment' section. Policy CSP - UserRights - Windows Client Management | Microsoft Docs

Default Value:

Administrators, LOCAL SERVICE, NETWORK SERVICE, SERVICE.

See Also

https://workbench.cisecurity.org/benchmarks/14664

Item Details

Plugin: Windows

Control ID: 316c79c2b32183c5863bdd4aa461cffc715304ad91882df5ad0f6b2b99b9aec0