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1.4 Ensure 'application pool identity' is configured for all application pools

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Information

Application Pool Identities are the actual users/authorities that will run the worker process - w3wp.exe. Assigning the correct user authority will help ensure that applications can function properly, while not giving overly permissive permissions on the system. These identities can further be used in ACLs to protect system content. It is recommended that each Application Pool run under a unique identity.
IIS has additional built-in least privilege identities intended for use by Application Pools. It is recommended that the default Application Pool Identity be changed to a least privilege principle other than Network Service. Furthermore, it is recommended that all application pool identities be assigned a unique least privilege principal.
To achieve isolation in IIS, application pools can be run as separate identities. IIS can be configured to automatically use the application pool identity if no anonymous user account is configured for a Web site. This can greatly reduce the number of accounts needed for Web sites and make management of the accounts easier. It is recommended the Application Pool Identity be set as the Anonymous User Identity.
The name of the Application Pool account corresponds to the name of the Application Pool. Application Pool Identities were introduced in Windows Server 2008 SP2. It is recommended that Application Pools be set to run as ApplicationPoolIdentity unless there is an underlying reason that the application pool needs to run as a specified end user account. One example where this is needed is for web farms using Kerberos authentication.
Rationale:
Setting Application Pools to use unique least privilege identities such as ApplicationPoolIdentity reduces the potential harm the identity could cause should the application ever become compromised.
Additionally, it will simplify application pools configuration and account management.

Solution

The default Application Pool identity may be set for an application using the IIS Manager GUI, using AppCmd.exe commands in a command-line window, directly editing the configuration files, or by writing WMI scripts. Perform the following to change the default identity to the built-in ApplicationPoolIdentity in the IIS Manager GUI:
1. Open the IIS Manager GUI
2. In the connections pane, expand the server node and click Application Pools
3. On the Application Pools page, select the DefaultAppPool, and then click Advanced Settings in the Actions pane
4. For the Identity property, click the '...' button to open the Application Pool Identity dialog box
5. Select the Built-in account option choose ApplicationPoolIdentity from the list, or input a unique application user created for this purpose
6. Restart IIS
To change the ApplicationPool identity to the built-in ApplicationPoolIdentity using AppCmd.exe, run the following from a command prompt:
%systemroot%\system32\inetsrv\appcmd set config /section:applicationPools /[name='<your apppool>'].processModel.identityType:ApplicationPoolIdentity
The example code above will set just the DefaultAppPool. Run this command for each configured Application Pool. Additionally, ApplicationPoolIdentity can be made the default for all Application Pools by using the Set Application Pool Defaults action on the Application Pools node.
If using a custom defined Windows user such as a dedicated service account, that user will need to be a member of the IIS_IUSRS group. The IIS_IUSRS group has access to all the necessary file and system resources so that an account, when added to this group, can seamlessly act as an application pool identity.
Default Value:
By Default, the DefaultAppPool in IIS is configured to use the ApplicationPoolIdentity account.

See Also

https://workbench.cisecurity.org/files/2220

Item Details

Category: ACCESS CONTROL

References: 800-53|AC-6, CSCv7|18

Plugin: Windows

Control ID: 1d67ee0efc17736e59f4d5feed7a34e8a292120ba6d4dcd96dfea810d8cc9a89