Modify Security Policies in Default Domain Controllers Policy

Applies To: Windows Server 2008, Windows Server 2008 R2

To increase security, domain controllers that run Windows Server 2008 and Windows Server 2008 R2 require (by default) that all client computers attempting to authenticate to them perform Server Message Block (SMB) packet signing and secure channel signing. If your production environment includes client computers that run platforms that do not support SMB packet signing (for example, Microsoft Windows NT® 4.0 with Service Pack 2 (SP2)) or if it includes client computers that run platforms that do not support secure channel signing (for example, Windows NT 4.0 with Service Pack 3 (SP3)), you might have to modify default security policies to ensure that client computers running older versions of the Windows operating system or non-Microsoft operating systems will be able to access domain resources in the upgraded domain.

To configure a domain controller to not require SMB packet signing or secure channel signing, disable the following settings in the Default Domain Controllers Policy:

• Microsoft network server: Digitally sign communications (always)

• Domain member: Digitally encrypt or sign secure channel data (always)

Back up the Default Domain Controllers Policy Group Policy object (GPO) before you modify it. Use the Group Policy Management Console (GPMC) to back up the GPO so that it can be restored, if necessary.

Membership in Domain Admins or Enterprise Admins, or equivalent, is the minimum required to complete this procedure. Review details about using the appropriate accounts and group memberships at Local and Domain Default Groups (https://go.microsoft.com/fwlink/?LinkId=83477).

To disable SMB packet signing enforcement based domain controllers

1. To open GPMC, click Start, click Run, type gpmc.msc, and then click OK.

2. In the console tree, right-click Default Domain Controllers Policy in Domains\Current Domain Name\Group Policy objects\Default Domain Controllers Policy, and then click Edit.

3. In the Group Policy Management Editor window, in the console tree, go to Computer Configuration/Policies/Windows Settings/Security Settings/Local Policies/Security Options.

4. In the details pane, double-click Microsoft network server: Digitally sign communications (always).

5. Verify that the Define this policy setting check box is selected, click Disabled to prevent SMB packet signing from being required, and then click OK.

   To apply the Group Policy change immediately, either restart the domain controller or open a command prompt, type the following command, and then press ENTER:

   gpupdate /force

Membership in Domain Admins or Enterprise Admins, or equivalent, is the minimum required to complete this procedure. Review details about using the appropriate accounts and group memberships at Local and Domain Default Groups (https://go.microsoft.com/fwlink/?LinkId=83477).

To disable secure channel signing enforcement on domain controllers

1. To open GPMC, click Start, click Run, type gpmc.msc, and then click OK.

2. In the console tree, right-click Default Domain Controllers Policy in Domains/Current Domain Name/Group Policy objects/Default Domain Controllers Policy, and then click Edit.

3. In the Group Policy Management Editor window, in the console tree, go to Computer Configuration/Policies/Windows Settings/Security Settings/Local Policies/Security Options.

4. In the details pane, double-click Domain member: Digitally encrypt or sign secure channel data (always), click Disabled to prevent secure channel signing from being required, and then click OK.

   To apply the Group Policy change immediately, either restart the domain controller or open a command prompt, type the following command, and then press ENTER:

   gpupdate /force

For more information about SMB packet signing and secure channel signing, see Appendix A: Background Information for Upgrading Active Directory Domains.

By default, domain controllers that run Windows Server 2008 and Windows Server 2008 R2 also prohibit clients running non-Microsoft operating systems or Windows NT 4.0 operating systems to establish security channels using weak Windows NT 4.0–style cryptography algorithms. Any security-channel-dependent operation that is initiated by clients running older versions of the Windows operating system or running non-Microsoft operating systems that do not support strong cryptographic algorithms will fail against a domain controller that runs Windows Server 2008 or Windows Server 2008 R2 with default settings.

Until you are able to upgrade all of the clients in your infrastructure, you can temporarily relax this requirement by modifying the following Default Domain Controllers Policy setting on domain controllers that run Windows Server 2008 or Windows Server 2008 R2. However, any operation that requires a secure channel between Windows NT 4 and Windows Server 2003 or later is not tested or supported. In addition, Windows Server 2008 R2 will not create an outbound trust to a Windows NT 4 domain. For more information, see article 942564 in the Microsoft Knowledge Base (https://go.microsoft.com/fwlink/?LinkId=190578).

• Allow cryptography algorithms compatible with Windows NT 4.0

Membership in Domain Admins or Enterprise Admins, or equivalent, is the minimum required to complete this procedure. Review details about using the appropriate accounts and group memberships at Local and Domain Default Groups (https://go.microsoft.com/fwlink/?LinkId=83477).

To allow cryptography algorithms that are compatible with Windows NT 4.0

1. To open GPMC, click Start, click Run, type gpmc.msc, and then click OK.

2. In the console tree, right-click Default Domain Controllers Policy in Domains/Current Domain Name/Group Policy objects/Default Domain Controllers Policy, and then click Edit.

3. In the Group Policy Management Editor window, in the console tree, go to Computer Configuration/Administrative Templates: Policy definitions (ADMX files) retrieved from the local machine/System/Net Logon.

4. In the details pane, double-click Allow cryptography algorithms compatible with Windows NT 4.0, and then click Enabled.

To apply the Group Policy change immediately, either restart the domain controller or open command line, type the following command, and then press ENTER:

`gpupdate /force`

For more information, see Effects of netlogon cryptographic support changes in Windows Server 2008 (https://go.microsoft.com/fwlink/?LinkId=106380). For more information about additional security policy changes in Windows 7 and Windows Server 2008 R2, see Secure default settings in Windows Server 2008 and Windows Server 2008 R2.

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