Client, service, and program issues can occur if you change security settings and user rights assignments

Windows XP

To increase the awareness of misconfigured security settings, use the Group Policy Object Editor tool to change security settings. When you use Group Policy Object Editor, user rights assignments are enhanced on the following operating systems:

• Windows XP Professional Service Pack 2 (SP2)

• Windows Server 2003 Service Pack 1 (SP1)

The enhanced feature is a dialog box that contains a link to this article. The dialog box appears when you change a security setting or a user rights assignment to a setting that offers less compatibility and is more restrictive. If you directly change the same security setting or user rights assignment by using the registry or by using security templates, the effect is the same as changing the setting in Group Policy Object Editor. However, the dialog box that contains the link to this article does not appear.

This article contains examples of clients, programs, and operations that are affected by specific security settings or user rights assignments. However, the examples are not authoritative for all Microsoft operating systems, for all third-party operating systems, or for all program versions that are affected. Not all security settings and user rights assignments are included in this article.

We recommend that you validate the compatibility of all security-related configuration changes in a test forest before you introduce them in a production environment. The test forest must mirror the production forest in the following ways:

• Client and server operating system versions, client and server programs, service pack versions, hotfixes, schema changes, security groups, group memberships, permissions on objects in the file system, shared folders, the registry, Active Directory directory service, local and Group Policy settings, and object count type and location

• Administrative tasks that are performed, administrative tools that are used, and operating systems that are used to perform administrative tasks

• Operations that are performed, such as the following:

  • Computer and user logon authentication

  • Password resets by users, by computers, and by administrators

  • Browsing

  • Setting permissions for the file system, for shared folders, for the registry, and for Active Directory resources by using ACL Editor in all client operating systems in all account or resource domains from all client operating systems from all account or resource domains

  • Printing from administrative and nonadministrative accounts

Windows Server 2003 SP1

User rights

The following list describes a user right, identifies configuration settings that may cause issues, describes why you should apply the user right and why you may want to remove the user right, and provides examples of compatibility issues that may occur when the user right is configured.

1. Access this computer from network

   1. Background
      
      The ability to interact with remote Windows-based computers requires the Access this computer from network user right. Examples of such network operations include the following:

      • Replication of Active Directory between domain controllers in a common domain or forest

      • Authentication requests to domain controllers from users and from computers

      • Access to shared folders, printers, and other system services that are located on remote computers on the network

      
      
      Users, computers, and service accounts gain or lose the Access this computer from network user right by being explicitly or implicitly added or removed from a security group that has been granted this user right. For example, a user account or a computer account may be explicitly added to a custom security group or a built-in security group by an administrator, or may be implicitly added by the operating system to a computed security group such as Domain Users, Authenticated Users, or Enterprise Domain Controllers.
      
      By default, user accounts and computer accounts are granted the Access this computer from network user right when computed groups such as Everyone or, preferably, Authenticated Users and, for domain controllers, the Enterprise Domain Controllers group, are defined in the default domain controllers Group Policy Object (GPO).

   2. Risky configurations
      
      The following are harmful configuration settings:

      • Removing the Enterprise Domain Controllers security group from this user right

      • Removing the Authenticated Users group or an explicit group that allows users, computers, and service accounts the user right to connect to computers over the network

      • Removing all users and computers from this user right

   3. Reasons to grant this user right

      • Granting the Access this computer from network user right to the Enterprise Domain Controllers group satisfies authentication requirements that Active Directory replication must have for replication to occur between domain controllers in the same forest.

      • This user right allows users and computers to access shared files, printers, and system services, including Active Directory.

      • This user right is required for users to access mail by using early versions of Microsoft Outlook Web Access (OWA).

   4. Reasons to remove this user right

      • Users who can connect their computers to the network can access resources on remote computers that they have permissions for. For example, this user right is required for a user to connect to shared printers and to folders. If this user right is granted to the Everyone group, and if some shared folders have both share and NTFS file system permissions configured so that the same group has read access, anyone can view files in those shared folders. However, this is an unlikely situation for fresh installations of Windows Server 2003 because the default share and the NTFS permissions in Windows Server 2003 do not include the Everyone group. For systems that are upgraded from Microsoft Windows NT 4.0 or Windows 2000, this vulnerability may have a higher level of risk because the default share and the file system permissions for these operating systems are not as restrictive as the default permissions in Windows Server 2003.

      • There is no valid reason for removing Enterprise Domain Controllers group from this user right.

      • The Everyone group is generally removed in favor of the Authenticated Users group. If the Everyone group is removed, the Authenticated Users group must be granted this user right.

      • Windows NT 4.0 domains that are upgraded to Windows 2000 do not explicitly grant the Access this computer from network user right to the Everyone group, the Authenticated Users group, or the Enterprise Domain Controllers group. Therefore, when you remove the Everyone group from Windows NT 4.0 domain policy, Active Directory replication will fail with an "Access Denied" error message after you upgrade to Windows 2000. Winnt32.exe in Windows Server 2003 avoids this misconfiguration by granting the Enterprise Domain Controllers group this user right when you upgrade Windows NT 4.0 primary domain controllers (PDCs). Grant the Enterprise Domain Controllers group this user right if it is not present in the Group Policy Object Editor.

   5. Examples of compatibility problems

      • Windows 2000 and Windows Server 2003: Replication of the following partitions will fail with "Access Denied" errors as reported by monitoring tools such as REPLMON and REPADMIN or replication events in the event log.

        • Active Directory Schema partition

        • Configuration partition

        • Domain partition

        • Global catalog partition

        • Application partition

      • All Microsoft network operating systems: User Account authentication from remote network client computers will fail unless the user or a security group that the user is a member of has been granted this user right.

      • All Microsoft network operating systems: Account authentication from remote network clients will fail unless the account or a security group the account is a member of has been granted this user right. This scenario applies to user accounts, to computer accounts, and to service accounts.

      • All Microsoft network operating systems: Removing all accounts from this user right will prevent any account from logging on to the domain or from accessing network resources. If computed groups such as Enterprise Domain Controllers, Everyone, or Authenticated Users are removed, you must explicitly grant this user right to accounts or to security groups that the account is a member of to access remote computers over the network. This scenario applies to all user accounts, to all computer accounts, and to all service accounts.

      • All Microsoft network operating systems: The local administrator account uses a "blank" password. Network connectivity with blank passwords is not permitted for administrator accounts in a domain environment. With this configuration, you can expect to receive an "Access Denied" error message.

2. Allow log on locally

   1. Background
      
      Users who are trying to log on at the console of a Windows-based computer (by using the CTRL+ALT+DELETE keyboard shortcut) and accounts who are trying to start a service must have local logon privileges on the hosting computer. Examples of local logon operations include administrators who are logging on to the consoles of member computers, or domain controllers throughout the enterprise and domain users who are logging on to member computers to access their desktops by using non-privileged accounts. Users who use a Remote Desktop connection or Terminal Services must have the Allow log on locally user right on destination computers that are running Windows 2000 or Windows XP because these logon modes are considered local to the hosting computer. Users who are logging on to a server that has Terminal Server enabled and who do not have this user right can still start a remote interactive session in Windows Server 2003 domains if they have the Allow logon through Terminal Services user right.

   2. Risky configurations
      
      The following are harmful configuration settings:

      • Removing administrative security groups, including Account Operators, Backup Operators, Print Operators or Server Operators, and the built-in Administrators group from the default domain controller's policy.

      • Removing service accounts that are used by components and by programs on member computers and on domain controllers in the domain from the default domain controller's policy.

      • Removing users or security groups that log on to the console of member computers in the domain.

      • Removing service accounts that are defined in the local Security Accounts Manager (SAM) database of member computers or of workgroup computers.

      • Removing non-built-in administrative accounts that are authenticating over Terminal Services that is running on a domain controller.

      • Adding all user accounts in the domain explicitly or implicitly through the Everyone group to the Deny logon locally logon right. This configuration will prevent users from logging on to any member computer or to any domain controller in the domain.

   3. Reasons to grant this user right

      • Users must have the Allow log on locally user right to access the console or the desktop of a workgroup computer, a member computer, or a domain controller.

      • Users must have this user right to log on over a Terminal Services session that is running on a Window 2000-based member computer or domain controller.

   4. Reasons to remove this user right

      • Failure to restrict console access to legitimate user accounts could result in unauthorized users downloading and executing malicious code to change their user rights.

      • Removal of the Allow log on locally user right prevents unauthorized logons on the consoles of computers, such as domain controllers or application servers.

      • Removal of this logon right prevents non-domain accounts from logging on at the console of member computers in the domain.

   5. Examples of compatibility problems

      • Windows 2000 terminal servers: The Allow log on locally user right is required for users to log on to Windows 2000 terminal servers.

      • Windows NT 4.0, Windows 2000, Windows XP, or Windows Server 2003: User accounts must be granted this user right to log on at the console of computers that are running Windows NT 4.0, Windows 2000, Windows XP, or Windows Server 2003.

      • Windows NT 4.0 and later: On computers that are running Windows NT 4.0 and later, if you add the Allow log on locally user right, but you implicitly or explicitly also grant the Deny logon locally logon right, the accounts will not be able to log on to the console of the domain controllers.

3. Bypass traverse checking

   1. Background
      
      The Bypass traverse checking user right allows the user to browse through folders in the NTFS file system or in the registry without checking for the Traverse Folder special access permission. The Bypass traverse checking user right does not allow the user to list the contents of a folder. It allows the user to traverse only its folders.

   2. Risky configurations
      
      The following are harmful configuration settings:

      • Removing non-administrative accounts that log on to Windows 2000-based Terminal Services computers or Windows Server 2003-based Terminal Services computers that do not have permissions to access files and folders in the file system.

      • Removing the Everyone group from the list of security principals who have this user right by default. Windows operating systems, and also many programs, are designed with the expectation that anyone who can legitimately access the computer will have the Bypass traverse checking user right. Therefore, removing the Everyone group from the list of security principals who have this user right by default could lead to operating system instability or to program failure. It is better that you leave this setting at its default.

   3. Reasons to grant this user right
      
      The default setting for the Bypass traverse checking user right is to allow anyone to bypass traverse checking. For experienced Windows system administrators, this is the expected behavior, and they configure file system access control lists (SACLs) accordingly. The only scenario where the default configuration may lead to a mishap is if the administrator who configures permissions does not understand the behavior and expects that users who cannot access a parent folder will not be able to access the contents of any child folders.

   4. Reasons to remove this user right
      
      To try to prevent access to the files or the folders in the file system, organizations that are very concerned about security may be tempted to remove the Everyone group, or even the Users group, from the list of groups that have the Bypass traverse checking user right.

   5. Examples of compatibility problems

      • Windows 2000, Windows Server 2003: If the Bypass traverse checking user right is removed or is misconfigured on computers that are running Windows 2000 or Windows Server 2003, Group Policy settings in the SYVOL folder will not replicate between domain controllers in the domain.

      • Windows 2000, Windows XP Professional, Windows Server 2003: Computers that are running Windows 2000, Windows XP Professional, or Windows Server 2003 will log events 1000 and 1202 and will not be able to apply computer policy and user policy when the required file system permissions are removed from the SYSVOL tree if the Bypass traverse checking user right is removed or is misconfigured.
        
         

      • Windows 2000, Windows Server 2003: On computers that are running Windows 2000 or Windows Server 2003, the Quota tab in Windows Explorer will disappear when you view properties on a volume.

      • Windows 2000: Non-administrators who log on to a Windows 2000 terminal server may receive the following error message:

        Userinit.exe application error. The application failed to initialize properly 0xc0000142 click OK to terminate the app.

      • Windows NT 4.0, Windows 2000, Windows XP, Windows Server 2003: Users whose computers are running Windows NT 4.0, Windows 2000, Windows XP, or Windows Server 2003 may not be able to access shared folders or files on shared folders, and they may receive "Access Denied" error messages if they are not granted the Bypass traverse checking user right.
        
        
         

      • Windows NT 4.0: On Windows NT 4.0-based computers, removal of the Bypass traverse checking user right will cause a file copy to drop file streams. If you remove this user right, when a file is copied from a Windows client or from a Macintosh client to a Windows NT 4.0 domain controller that is running Services for Macintosh, the destination file stream is lost, and the file appears as a text-only file.

      • Microsoft Windows 95, Microsoft Windows 98: On a client computer that is running Windows 95 or Windows 98, the net use * /home command will fail with an "Access Denied" error message if the Authenticated Users group is not granted the Bypass traverse checking user right.

      • Outlook Web Access: Non-administrators will not be able to log on to Microsoft Outlook Web Access, and they will receive an "Access Denied" error message if they are not granted the Bypass traverse checking user right.

Security Settings

The following list identifies a security setting, and the nested list provides a description about the security setting, identifies configuration settings that may cause issues, describes why you should apply the security setting, and then describes reasons why you may want to remove the security setting. The nested list then provides a symbolic name for the security setting and the registry path of the security setting. Finally, examples are provided of compatibility issues that may occur when the security setting is configured.

1. Audit: Shut down system immediately if unable to log security audits

   1. Background

      • The Audit: Shut down system immediately if unable to log security audits setting determines whether the system shuts down if you cannot log security events. This setting is required for the Trusted Computer Security Evaluation Criteria (TCSEC) program's C2 evaluation and for the Common Criteria for Information Technology Security Evaluation to prevent auditable events if the audit system can't log those events. If the auditing system fails, the system is shut down, and a Stop error message appears.

      • If the computer cannot record events to the security log, critical evidence or important troubleshooting information may not be available for review after a security incident.

   2. Risky configuration
      
      The following is a harmful configuration setting: The Audit: Shut down system immediately if unable to log security audits setting is turned on, and the size of the security event log is constrained by the Do not overwrite events (clear log manually) option, the Overwrite Events as needed option, or the Overwrite Events older than number days option in Event Viewer. See the "Examples of Compatibility Problems" section for information about specific risks for computers that are running the original released version of Windows 2000, Windows 2000 Service Pack 1 (SP1), Windows 2000 SP2, or Windows 2000 SP3.

   3. Reasons to enable this setting
      
      If the computer cannot record events to the security log, critical evidence or important troubleshooting information may not be available for review after a security incident.

   4. Reasons to disable this setting

      • Enabling the Audit: Shut down system immediately if unable to log security audits setting stops the system if a security audit cannot be logged for any reason. Typically, an event cannot be logged when the security audit log is full and when its specified retention method is either the Do not overwrite events (clear log manually) option or the Overwrite Events older than number days option.

      • The administrative burden of enabling the Audit: Shut down system immediately if unable to log security audits setting can be very high, especially if you also turn on the Do not overwrite events (clear log manually) option for the security log. This setting provides for individual accountability of operator actions. For example, an administrator could reset permissions on all users, computers, and groups in an organizational unit (OU) where auditing was enabled by using the built-in administrator account or other shared account and then deny that they reset such permissions. However, enabling the setting does reduce the robustness of the system because a server may be forced to shut down by overwhelming it with logon events and with other security events that are written to the security log. Additionally, because the shutdown is not graceful, irreparable damage to the operating system, programs, or data may result. While NTFS guarantees that the file system’s integrity is maintained during an ungraceful system shutdown, it cannot guarantee that every data file for every program will still be in a usable form when the system restarts.

   5. Symbolic Name:
      
      CrashOnAuditFail

   6. Registry Path:

      HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa\CrashOnAuditFail (Reg_DWORD)

   7. Examples of compatibility problems

      • Windows 2000: Because of a bug, computers that are running the original released version of Windows 2000, Windows 2000 SP1, Windows 2000 SP2, or Windows Server SP3 may stop logging events before the size that is specified in the Maximum log size option for the security event log is reached. This bug is fixed in Windows 2000 Service Pack 4 (SP4). Make sure that your Windows 2000 domain controllers have Windows 2000 Service Pack 4 installed before you consider enabling this setting.
        
         

      • Windows 2000, Windows Server 2003: Computers that are running Windows 2000 or Windows Server 2003 may stop responding and then may spontaneously restart if the Audit: Shut down system immediately if unable to log security audits setting is turned on, the security log is full, and an existing event log entry cannot be overwritten. When the computer restarts, the following Stop error message appears:

        STOP: C0000244 {Audit Failed}
        An attempt to generate a security audit failed.

        To recover, an administrator must log on, archive the security log (optional), clear the security log, and then reset this option (optional and as-needed).

      • Microsoft Network Client for MS-DOS, Windows 95, Windows 98, Windows NT 4.0, Windows 2000, Windows XP, Windows Server 2003: Non-administrators who try to log on to a domain will receive the following error message:

        Your account is configured to prevent you from using this computer. Please try another computer.

      • Windows 2000: On Windows 2000-based computers, non-administrators will not be able to log on to remote access servers, and they will receive an error message that is similar to the following:

        Unknown user or bad password

      • Windows 2000: On Windows 2000 domain controllers, the Intersite Messaging service (Ismserv.exe) will stop and cannot be restarted. DCDIAG will report the error as "failed test services ISMserv," and event ID 1083 will be registered in the event log.

      • Windows 2000: On Windows 2000 domain controllers, Active Directory replication will fail, and an "Access Denied" message will appear if the security event log is full.

      • Microsoft Exchange 2000: Servers that are running Exchange 2000 will not be able to mount the information store database, and event 2102 will be registered in the event log.

      • Outlook, Outlook Web Access: Non-administrators will not be able to access their mail through Microsoft Outlook or through Microsoft Outlook Web Access, and they will receive a 503 error.

2. Domain controller: LDAP server signing requirements

   1. Background
      
      The Domain controller: LDAP server signing requirements security setting determines whether the Lightweight Directory Access Protocol (LDAP) server requires LDAP clients to negotiate data signing. The possible values for this policy setting are as follows:

      • None: Data signing is not required to bind with the server. If the client requests data signing, the server supports it.

      • Require signing: The LDAP data-signing option must be negotiated unless Transport Layer Security/Secure Socket Layer (TLS/SSL) is being used.

      • not defined: This setting is not enabled or disabled.

   2. Risky configurations
      
      The following are harmful configuration settings:

      • Enabling Require signing in environments where clients do not support LDAP signing or where client-side LDAP signing is not enabled on the client

      • Applying the Windows 2000 or the Windows Server 2003 Hisecdc.inf security template in environments where the clients do not support LDAP signing or where client-side LDAP signing is not enabled

      • Applying the Windows 2000 or the Windows Server 2003 Hisecws.inf security template in environments where the clients do not support LDAP signing or where client-side LDAP signing is not enabled

   3. Reasons to enable this setting
      
      Unsigned network traffic is susceptible to man-in-the-middle attacks where an intruder captures packets between the client and the server, modifies the packets, and then forwards them to the server. When this behavior occurs on an LDAP server, an attacker could cause a server to make decisions that are based on false queries from the LDAP client. You can lower this risk in a corporate network by implementing strong physical security measures to help protect the network infrastructure. Internet Protocol security (IPSec) authentication header mode can help prevent man-in-the-middle attacks. Authentication header mode performs mutual authentication and packet integrity for IP traffic.

   4. Reasons to disable this setting

      • Clients that do not support LDAP signing will not be able to carry out LDAP queries against domain controllers and against global catalogs if NTLM authentication is negotiated and if the correct service packs are not installed on Windows 2000 domain controllers.

      • Network traces of LDAP traffic between clients and servers will be encrypted. This makes it difficult to examine LDAP conversations.

      • Windows 2000-based servers must have Windows 2000 Service Pack 3 (SP3) or installed when they are administered with programs that support LDAP signing that are run from client computers that run Windows 2000 SP4, Windows XP, or Windows Server 2003.  

   5. Symbolic Name:
      
      LDAPServerIntegrity

   6. Registry Path:

      HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\NTDS\Parameters\LDAPServerIntegrity (Reg_DWORD)

   7. Examples of compatibility problems

      • Simple binds will fail, and you will receive the following error message:

        Ldap_simple_bind_s() failed: Strong Authentication Required.

      • Windows 2000 Service Pack 4, Windows XP, Windows Server 2003: On clients that are running Windows 2000 SP4, Windows XP, or Windows Server 2003, some Active Directory administration tools will not operate correctly against domain controllers that are running versions of Windows 2000 that are earlier than SP3 when NTLM authentication is negotiated.
        
         

      • Windows 2000 Service Pack 4, Windows XP, Windows Server 2003: On clients that are running Windows 2000 SP4, Windows XP, or Windows Server 2003, some Active Directory administration tools that target domain controllers that are running versions of Windows 2000 that are earlier than SP3 will not operate correctly if they are using IP addresses (for example, "dsa.msc /server=x.x.x.x" where
        x.x.x.x is an IP address).
        
        
         

      • Windows 2000 Service Pack 4, Windows XP, Windows Server 2003: On clients that are running Windows 2000 SP4, Windows XP, or Windows Server 2003, some Active Directory administration tools that target domain controllers that are running versions of Windows 2000 that are earlier than SP3 will not operate correctly.
        
         

3. Domain member: Require strong (Windows 2000 or later) session key

   1. Background

      • The Domain member: Require strong (Windows 2000 or later) session key setting determines whether a secure channel can be established with a domain controller that cannot encrypt secure channel traffic with a strong, 128-bit session key. Enabling this setting prevents establishing a secure channel with any domain controller that cannot encrypt secure channel data with a strong key. Disabling this setting allows 64-bit session keys.

      • Before you can enable this setting on a member workstation or on a server, all domain controllers in the domain that the member belongs to must be able to encrypt secure channel data with a strong, 128-bit key. This means that all such domain controllers must be running Windows 2000 or later.

   2. Risky configuration
      
      Enabling the Domain member: Require strong (Windows 2000 or later) session key setting is a harmful configuration setting.

   3. Reasons to enable this setting

      • Session keys that are used to establish secure channel communications between member computers and domain controllers are much stronger in Windows 2000 than they are in earlier versions of Microsoft operating systems.

      • When it's possible, it is a good idea to take advantage of these stronger session keys to help protect secure channel communications from eavesdropping and from session hijacking network attacks. Eavesdropping is a form of malicious attack where network data is read or is altered in transit. The data can be modified to hide or to change the sender, or to redirect it.

      Important A computer that is running Windows Server 2008 R2 or Windows 7 supports only strong keys when secure channels are used. This restriction prevents a trust between any Windows NT 4.0-based domain and any Windows Server 2008 R2-based domain. Additionally, this restriction blocks the Windows NT 4.0-based domain membership of computers that are running Windows 7 or Windows Server 2008 R2, and vice versa.

   4. Reasons to disable this setting
      
      The domain contains member computers that are running operating systems other than Windows 2000, Windows XP, or Windows Server 2003.

   5. Symbolic Name:
      
      StrongKey

   6. Registry Path:

      HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Netlogon\Parameters\RequireStrongKey (Reg_DWORD)

   7. Examples of compatibility problems
      
      Windows NT 4.0: On Windows NT 4.0-based computers, resetting secure channels of trust relationships between Windows NT 4.0 and Windows 2000 domains with NLTEST fails. An "Access Denied" error message appears:

      The trust relationship between the primary domain and the trusted domain failed.
      
      Windows 7 and Server 2008 R2: For Windows 7 and later versions and Windows Server 2008 R2 and later versions, this setting is not honored any longer and the strong key is used always. Because of that, trusts with Windows NT 4.0 domains do not work any longer.

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

   1. Background

      • Enabling Domain member: Digitally encrypt or sign secure channel data (always) prevents establishing a secure channel with any domain controller that cannot sign or encrypt all secure channel data. To help protect authentication traffic from man-in-the-middle attacks, replay attacks, and other kinds of network attacks, Windows-based computers create a communication channel that is known as a secure channel through the Net Logon service to authenticate computer accounts. Secure channels are also used when a user in one domain connects to a network resource in a remote domain. This multidomain authentication, or pass-through authentication, allows a Windows-based computer that has joined a domain to have access to the user account database in its domain and in any trusted domains.

      • To enable the Domain member: Digitally encrypt or sign secure channel data (always) setting on a member computer, all domain controllers in the domain that the member belongs to must be able to sign or encrypt all secure channel data. This means that all such domain controllers must be running Windows NT 4.0 with Service Pack 6a (SP6a) or later.

      • Enabling the Domain member: Digitally encrypt or sign secure channel data (always) setting automatically enables the Domain member: Digitally encrypt or sign secure channel data (when possible) setting.

   2. Risky configuration
      
      Enabling the Domain member: Digitally encrypt or sign secure channel data (always) setting in domains where not all domain controllers can sign or encrypt secure channel data is a harmful configuration setting.

   3. Reasons to enable this setting
      
      Unsigned network traffic is susceptible to man-in-the-middle attacks, where an intruder captures packets between the server and the client and then modifies them before forwarding them to the client. When this behavior occurs on an Lightweight Directory Access Protocol (LDAP) server, the intruder could cause a client to make decisions that are based on false records from the LDAP directory. You can lower the risk of such an attack on a corporate network by implementing strong physical security measures to help protect the network infrastructure. Additionally, implementing Internet Protocol security (IPSec) authentication header mode can help prevent man-in-the-middle attacks. This mode performs mutual authentication and packet integrity for IP traffic.

   4. Reasons to disable this setting

      • Computers in local or external domains do support encrypted secure channels.

      • Not all domain controllers in the domain have the appropriate service pack revision levels to support encrypted secure channels.

   5. Symbolic Name:
      
      StrongKey

   6. Registry Path:

      HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Netlogon\Parameters\RequireSignOrSeal (REG_DWORD)

   7. Examples of compatibility problems

      • Windows NT 4.0: Windows 2000-based member computers will not be able to join Windows NT 4.0 domains and will receive the following error message:

        The account is not authorized to log in from this station.

        For more information, click the following article number to view the article in the Microsoft Knowledge Base:

        281648 Error message: The account is not authorized to login from this station
         

      • Windows NT 4.0: Windows NT 4.0 domains will not be able to establish a down-level trust with a Windows 2000 domain and will receive the following error message:

        The account is not authorized to log in from this station.

        Existing down-level trusts may also not authenticate users from the trusted domain. Some users may have problems logging on to the domain, and they may receive an error message that states that the client cannot find the domain.

      • Windows XP: Windows XP clients that are joined to Windows NT 4.0 domains will not be able to authenticate logon attempts and may receive the following error message, or the following events may be registered in the event log:

        Windows cannot connect to the domain either because the domain controller is down or is otherwise unavailable or because your computer account was not found

      • Microsoft Network: Microsoft Network clients will receive one of the following error messages:

        Logon failure: unknown username or bad password.

        There is no user session key for the specified logon session.

5. Microsoft network client: Digitally sign communications (always)

   1. Background
      
      Server Message Block (SMB) is the resource-sharing protocol that is supported by many Microsoft operating systems. It is the basis of network basic input/output system (NetBIOS) and of many other protocols. SMB signing authenticates both the user and the server that hosts the data. If either side fails the authentication process, data transmission will not occur.
      
      Enabling SMB signing starts during SMB protocol negotiation. The SMB signing policies determine whether the computer always digitally signs client communications.
      
      The Windows 2000 SMB authentication protocol supports mutual authentication. Mutual authentication closes a "man-in-the-middle" attack. The Windows 2000 SMB authentication protocol also supports message authentication. Message authentication helps prevent active message attacks. To give you this authentication, SMB signing puts a digital signature into each SMB. The client and the server each verify the digital signature.
      
      To use SMB signing, you must enable SMB signing or require SMB signing on both the SMB client and the SMB server. If SMB signing is enabled on a server, clients that are also enabled for SMB signing use the packet signing protocol during all subsequent sessions. If SMB signing is required on a server, a client cannot establish a session unless the client is enabled or required for SMB signing.
      
      
      Enabling digital signing in high-security networks helps prevent the impersonation of clients and of servers. This kind of impersonation is known as session hijacking. An attacker who has access to the same network as the client or the server uses session hijacking tools to interrupt, end, or steal a session in progress. An attacker could intercept and modify unsigned SMB packets, modify the traffic, and then forward it so that the server might perform unwanted actions. Or, the attacker could pose as the server or as the client after a legitimate authentication and then gain unauthorized access to data.
      
      The SMB protocol that is used for file sharing and for print sharing in computers that are running Windows 2000 Server, Windows 2000 Professional, Windows XP Professional, or Windows Server 2003 supports mutual authentication. Mutual authentication closes session hijacking attacks and supports message authentication. Therefore, it prevents man-in-the-middle attacks. SMB signing provides this authentication by placing a digital signature in each SMB. The client and the server then verify the signature.
      
      Notes

      • As an alternative countermeasure, you can enable digital signatures with IPSec to help protect all network traffic. There are hardware-based accelerators for IPSec encryption and signing that you can use to minimize the performance impact from the server's CPU. There are no such accelerators that are available for SMB signing.
        
        For more information, see the Digitally sign server communications chapter on the Microsoft MSDN website.
        
        Configure SMB signing through Group Policy Object Editor because a change to a local registry value has no effect if there is an overriding domain policy.

      • In Windows 95, Windows 98, and Windows 98 Second Edition, the Directory Services Client uses SMB signing when it authenticates with Windows Server 2003 servers by using NTLM authentication. However, these clients do not use SMB signing when they authenticate with these servers by using NTLMv2 authentication. Additionally, Windows 2000 servers do not respond to SMB signing requests from these clients. For more information, see item 10: "Network security: Lan Manager authentication level."

   2. Risky configuration
      
      The following is a harmful configuration setting: Leaving both the Microsoft network client: Digitally sign communications (always) setting and the Microsoft network client: Digitally sign communications (if server agrees) setting set to "Not Defined" or disabled. These settings allow the redirector to send plain text passwords to non-Microsoft SMB servers that do not support password encryption during authentication.

   3. Reasons to enable this setting
      
      Enabling Microsoft network client: Digitally sign communications (always) requires clients to sign SMB traffic when contacting servers that do not require SMB signing. This makes clients less vulnerable to session hijacking attacks.

   4. Reasons to disable this setting

      • Enabling Microsoft network client: Digitally sign communications (always) prevents clients from communicating with target servers that do not support SMB signing.

      • Configuring computers to ignore all unsigned SMB communications prevents earlier programs and operating systems from connecting.

   5. Symbolic Name:
      
      RequireSMBSignRdr

   6. Registry Path:

      HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanWorkstation\Parameters\RequireSecuritySignature

   7. Examples of compatibility problems

      • Windows NT 4.0: You will not be able to reset the secure channel of a trust between a Windows Server 2003 domain and a Windows NT 4.0 domain by using NLTEST or NETDOM, and you will receive an "Access Denied" error message.

      • Windows XP: Copying files from Windows XP clients to Windows 2000-based servers and to Windows Server 2003-based servers may take more time.

      • You will not be able to map a network drive from a client with this setting enabled, and you will receive the following error message:

        The account is not authorized to log in from this station.

   8. Restart requirements
      
      Restart the computer, or restart the Workstation service. To do this, type the following commands at a command prompt. Press Enter after you type each command.

      net stop workstation
      net start workstation

6. Microsoft network server: Digitally sign communications (always)

   1. Background

      • Server Messenger Block (SMB) is the resource-sharing protocol that is supported by many Microsoft operating systems. It is the basis of network basic input/output system (NetBIOS) and of many other protocols. SMB signing authenticates both the user and the server that hosts the data. If either side fails the authentication process, data transmission will not occur.
        
        Enabling SMB signing starts during SMB protocol negotiation. The SMB signing policies determine whether the computer always digitally signs client communications.
        
        The Windows 2000 SMB authentication protocol supports mutual authentication. Mutual authentication closes a "man-in-the-middle" attack. The Windows 2000 SMB authentication protocol also supports message authentication. Message authentication helps prevent active message attacks. To give you this authentication, SMB signing puts a digital signature into each SMB. The client and the server each verify the digital signature.
        
        To use SMB signing, you must enable SMB signing or require SMB signing on both the SMB client and the SMB server. If SMB signing is enabled on a server, clients that are also enabled for SMB signing use the packet signing protocol during all subsequent sessions. If SMB signing is required on a server, a client cannot establish a session unless the client is enabled or required for SMB signing.
        
        
        Enabling digital signing in high-security networks helps prevent the impersonation of clients and of servers. This kind of impersonation is known as session hijacking. An attacker who has access to the same network as the client or the server uses session hijacking tools to interrupt, end, or steal a session in progress. An attacker could intercept and modify unsigned Subnet Bandwidth Manager (SBM) packets, modify the traffic, and then forward it so that the server might perform unwanted actions. Or, the attacker could pose as the server or as the client after a legitimate authentication and then gain unauthorized access to data.
        
        The SMB protocol that is used for file sharing and for print sharing in computers that are running Windows 2000 Server, Windows 2000 Professional, Windows XP Professional, or Windows Server 2003 supports mutual authentication. Mutual authentication closes session hijacking attacks and supports message authentication. Therefore, it prevents man-in-the-middle attacks. SMB signing provides this authentication by placing a digital signature in each SMB. The client and the server then verify the signature.

      • As an alternative countermeasure, you can enable digital signatures with IPSec to help protect all network traffic. There are hardware-based accelerators for IPSec encryption and signing that you can use to minimize the performance impact from the server's CPU. There are no such accelerators that are available for SMB signing.

      • In Windows 95, Windows 98, and Windows 98 Second Edition, the Directory Services Client uses SMB signing when it authenticates with Windows Server 2003 servers by using NTLM authentication. However, these clients do not use SMB signing when they authenticate with these servers by using NTLMv2 authentication. Additionally, Windows 2000 servers do not respond to SMB signing requests from these clients. For more information, see item 10: "Network security: Lan Manager authentication level."

   2. Risky configuration
      
      The following is a harmful configuration setting: Enabling the Microsoft network server: Digitally sign communications (always) setting on servers and on domain controllers that are accessed by incompatible Windows-based computers and third-party operating system-based client computers in local or external domains.

   3. Reasons to enable this setting

      • All client computers that enable this setting directly through the registry or through the Group Policy setting support SMB signing. In other words, all client computers that have this setting enabled run either Windows 95 with the DS client installed, Windows 98, Windows NT 4.0, Windows 2000, Windows XP Professional, or Windows Server 2003.

      • If Microsoft network server: Digitally sign communications (always) is disabled, SMB signing is completely disabled. Completely disabling all SMB signing leaves computers more vulnerable to session hijacking attacks.

   4. Reasons to disable this setting

      • Enabling this setting may cause slower file copy and network performance on client computers.

      • Enabling this setting will prevent clients that cannot negotiate SMB signing from communicating with servers and with domain controllers. This causes operations such as domain joins, user and computer authentication, or network access by programs to fail.

   5. Symbolic Name:
      
      RequireSMBSignServer

   6. Registry Path:

      HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanManServer\Parameters\RequireSecuritySignature (REG_DWORD)

   7. Examples of compatibility problems

      • Windows 95: Windows 95 clients that do not have the Directory Services (DS) Client installed will fail logon authentication and will receive the following error message:

        The domain password you supplied is not correct, or access to your logon server has been denied.

      • Windows NT 4.0: Client computers that are running versions of Windows NT 4.0 that are earlier than Service Pack 3 (SP3) will fail logon authentication and will receive the following error message:

        The system could not log you on. Make sure your username and your domain are correct, then type your password again.

        Some non-Microsoft SMB servers support only unencrypted password exchanges during authentication. (These exchanges also known as "plain text" exchanges.) For Windows NT 4.0 SP3 and later versions, the SMB redirector does not send an unencrypted password during authentication to an SMB server unless you add a specific registry entry.
        To enable unencrypted passwords for the SMB client on Windows NT 4.0 SP 3 and newer systems, modify the registry as follows: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Rdr\Parameters
        
        Value Name: EnablePlainTextPassword
        
        Data Type: REG_DWORD
        
        Data: 1
        
         

      • Windows Server 2003: By default, security settings on domain controllers that run Windows Server 2003 are configured to help prevent domain controller communications from being intercepted or tampered with by malicious users. For users to successfully communicate with a domain controller that runs Windows Server 2003, client computers must use both SMB signing and encryption or secure channel traffic signing. By default, clients that run Windows NT 4.0 with Service Pack 2 (SP2) or earlier installed and clients that run Windows 95 do not have SMB packet signing enabled. Therefore, these clients may not be able to authenticate to a Windows Server 2003-based domain controller.

      • Windows 2000 and Windows Server 2003 policy settings: Depending on your specific installation needs and configuration, we recommend that you set the following policy settings at the lowest entity of necessary scope in the Microsoft Management Console Group Policy Editor snap-in hierarchy:

        • Computer Configuration\Windows Security Settings\Security Options

        • Send unencrypted password to connect to third-party SMB servers (this setting is for Windows 2000)

        • Microsoft network client: Send unencrypted password to third-party SMB servers (this setting is for Windows Server 2003)

        
        Note In some third-party CIFS servers, such as older Samba versions, you cannot use encrypted passwords.

      • The following clients are incompatible with the Microsoft network server: Digitally sign communications (always) setting:

        • Apple Computer, Inc., Mac OS X clients

        • Microsoft MS-DOS network clients (for example, Microsoft LAN Manager)

        • Microsoft Windows for Workgroups clients

        • Microsoft Windows 95 clients without the DS Client installed

        • Microsoft Windows NT 4.0-based computers without SP3 or later installed

        • Novell Netware 6 CIFS clients

        • SAMBA SMB clients that do not have support for SMB signing

   8. Restart requirements
      
      Restart the computer, or restart the Server service. To do this, type the following commands at a command prompt. Press Enter after you type each command.

      net stop server
      net start server

7. Network access: Allow anonymous SID/Name translation

   1. Background
      
      The Network access: Allow anonymous SID/Name translation security setting determines whether an anonymous user can request Security Identification Number (SID) attributes for another user.

   2. Risky configuration
      
      Enabling the Network access: Allow anonymous SID/Name translation setting is a harmful configuration setting.

   3. Reasons to enable this setting
      
      If the Network access: Allow anonymous SID/Name translation setting is disabled, earlier operating systems or applications may not be able to communicate with Windows Server 2003 domains. For example, the following operating systems, services, or applications may not work:

      • Windows NT 4.0-based Remote Access Service servers

      • Microsoft SQL Server that are running on Windows NT 3.x-based computers or Windows NT 4.0-based computers

      • Remote Access Service that is running on Windows 2000-based computers that are located in Windows NT 3.x domains or Windows NT 4.0 domains

      • SQL Server that is running on Windows 2000-based computers that are located in Windows NT 3.x domains or in Windows NT 4.0 domains

      • Users in Windows NT 4.0 resource domain who want to grant permissions to access files, shared folders, and registry objects to user accounts from account domains that contain Windows Server 2003 domain controllers

   4. Reasons to disable this setting
      
      If this setting is enabled, a malicious user could use the well-known Administrators SID to obtain the real name of the built-in Administrator account, even if the account has been renamed. That person could then use the account name to initiate a password-guessing attack.

   5. Symbolic Name: N/A

   6. Registry Path: None. The path is specified in UI code.

   7. Examples of compatibility problems
      
      Windows NT 4.0: Computers in Windows NT 4.0 resource domains will display the "Account Unknown" error message in ACL Editor if resources, including shared folders, shared files, and registry objects, are secured with security principals that reside in account domains that contain Windows Server 2003 domain controllers.

8. Network access: Do not allow anonymous enumeration of SAM accounts

   1. Background

      • The Network access: Do not allow anonymous enumeration of SAM accounts setting determines which additional permissions will be granted for anonymous connections to the computer. Windows allows anonymous users to perform certain activities, such as enumerating the names of workstation and server Security Accounts Manager (SAM) accounts and of network shares. For example, an administrator can use this to grant access to users in a trusted domain that does not maintain a reciprocal trust. Once a session is made, an anonymous user may have the same access that is granted to the Everyone group based on the setting in the Network access: Let Everyone permissions apply to anonymous users setting or the discretionary access control list (DACL) of the object.
        
        Typically, anonymous connections are requested by earlier versions of clients (down-level clients) during SMB session setup. In these cases, a network trace shows that the SMB Process ID (PID) is the client redirector such as 0xFEFF in Windows 2000 or 0xCAFE in Windows NT. RPC may also try to make anonymous connections.

      • Important This setting has no impact on domain controllers. On domain controllers, this behavior is controlled by the presence of "NT AUTHORITY\ANONYMOUS LOGON" in "Pre-Windows 2000 compatible Access".

      • In Windows 2000, a similar setting called Additional Restrictions for Anonymous Connections manages the RestrictAnonymous registry value. The location of this value is as follows

        HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\LSA  

   2. Risky configurations
      
      Enabling the Network access: Do not allow anonymous enumeration of SAM accounts setting is a harmful configuration setting from a compatibility perspective. Disabling it is a harmful configuration setting from a security perspective.

   3. Reasons to enable this setting
      
      An unauthorized user could anonymously list account names and then use the information to try to guess passwords or to perform social engineering attacks. Social engineering is jargon that means tricking people into revealing their passwords or some form of security information.

   4. Reasons to disable this setting
      
      If this setting is enabled, it is impossible to establish trusts with Windows NT 4.0 domains. This setting also causes problems with down-level clients (such as Windows NT 3.51 clients and Windows 95 clients) that are trying to use resources on the server.

   5. Symbolic Name:
      
      
      RestrictAnonymousSAM

   6. Registry Path:

      HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa\RestrictAnonymousSAM (Reg_DWORD)

   7. Examples of compatibility problems

   • SMS Network Discovery will not be able to obtain operating system information and will write "Unknown" in the OperatingSystemNameandVersion property.

   • Windows 95, Windows 98: Windows 95 clients and Windows 98 clients will not be able to change their passwords.

   • Windows NT 4.0: Windows NT 4.0-based member computers will not be able to be authenticated.

   • Windows 95, Windows 98: Windows 95-based and Windows 98-based computers will not be able to be authenticated by Microsoft domain controllers.

   • Windows 95, Windows 98: Users on Windows 95-based and Windows 98-based computers will not be able to change the passwords for their user accounts.

9. Network access: Do not allow anonymous enumeration of SAM accounts and shares

   1. Background

      • The Network access: Do not allow anonymous enumeration of SAM accounts and shares setting (also known as RestrictAnonymous) determines whether anonymous enumeration of Security Accounts Manager (SAM) accounts and shares is allowed. Windows allows anonymous users to perform certain activities, such as enumerating the names of domain accounts (users, computers, and groups) and of network shares. This is convenient, for example, when an administrator wants to grant access to users in a trusted domain that does not maintain a reciprocal trust. If you do not want to allow anonymous enumeration of SAM accounts and of shares, enable this setting.

      • In Windows 2000, a similar setting called Additional Restrictions for Anonymous Connections manages the RestrictAnonymous registry value. The location of this value is as follows:

        HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\LSA

   2. Risky configuration
      
      Enabling the Network access: Do not allow anonymous enumeration of SAM accounts and shares setting is a harmful configuration setting.

   3. Reasons to enable this setting

      • Enabling the Network access: Do not allow anonymous enumeration of SAM accounts and shares setting prevents enumeration of SAM accounts and shares by users and computers that are using anonymous accounts.

   4. Reasons to disable this setting

      • If this setting is enabled, an unauthorized user could anonymously list account names and then use the information to try to guess passwords or to perform social engineering attacks. Social engineering is jargon that means tricking people into revealing their password or some form of security information.

      • If this setting is enabled, it will be impossible to establish trusts with Windows NT 4.0 domains. This setting will also cause problems with down-level clients such as Windows NT 3.51 and Windows 95 clients that are trying to use resources on the server.

      • It will be impossible to grant access to users of resource domains because administrators in the trusting domain will not be able to enumerate lists of accounts in the other domain. Users who access file and print servers anonymously will not be able to list the shared network resources on those servers. The users must authenticate before they can view the lists of shared folders and printers.

   5. Symbolic Name:
      
      RestrictAnonymous

   6. Registry Path:

      HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa\RestrictAnonymous

   7. Examples of compatibility problems

      • Windows NT 4.0: Users will not be able to change their passwords from Windows NT 4.0 workstations when RestrictAnonymous is enabled on domain controllers in the users' domain.

      • Windows NT 4.0: Adding users or global groups from trusted Windows 2000 domains to Windows NT 4.0 local groups in User Manager will fail, and the following error message will appear:

        There are currently no logon servers available to service the logon request.

      • Windows NT 4.0: Windows NT 4.0-based computers will not be able to join domains during setup or by using the domain join user interface.

      • Windows NT 4.0: Establishing a down-level trust with Windows NT 4.0 resource domains will fail. The following error message will appear when RestrictAnonymous is enabled on the trusted domain:

        Could not find domain controller for this domain.

      • Windows NT 4.0: Users who log on to Windows NT 4.0-based Terminal Server computers will map to the default home directory instead of the home directory that is defined in User Manager for domains.

      • Windows NT 4.0: Windows NT 4.0 backup domain controllers (BDCs) will not be able to start the Net Logon service, obtain a list of backup browsers, or synchronize the SAM database from Windows 2000 or from Windows Server 2003 domain controllers in the same domain.

      • Windows 2000: Windows 2000-based member computers in Windows NT 4.0 domains will not be able to view printers in external domains if the No access without explicitly anonymous permissions setting is enabled in the local security policy of the client computer.

      • Windows 2000: Windows 2000 domain users will not be able to add network printers from Active Directory; however, they will be able to add printers after they select them from the tree view.

      • Windows 2000: On Windows 2000-based computers, ACL Editor will not be able to add users or global groups from trusted Windows NT 4.0 domains.

      • ADMT version 2: Password migration for user accounts that are migrated between forests with Active Directory Migration Tool (ADMT) version 2 will fail.
        
        For more information, click the following article number to view the article in the Microsoft Knowledge Base:

        322981 How to troubleshoot inter-forest password migration with ADMTv2

      • Outlook clients: The global address list will appear empty to Microsoft Exchange Outlook clients.

      • SMS: Microsoft Systems Management Server (SMS) Network Discovery will not be able to obtain the operating system information. Therefore, it will write "Unknown" in the OperatingSystemNameandVersion property of the SMS DDR property of the discovery data record (DDR).

      • SMS: When you use the SMS Administrator User Wizard to browse for users and groups, no users or groups will be listed. Additionally, Advanced clients cannot communicate with the Management Point. Anonymous access is required on the Management Point.

      • SMS: When you are using the Network Discovery feature in SMS 2.0 and in Remote Client Installation with the Topology, client, and client operating systems network discovery option turned on, computers may be discovered but may not be installed.

10. Network security: Lan Manager authentication level

    1. Background
       
       LAN Manager (LM) authentication is the protocol that is used to authenticate Windows clients for network operations, including domain joins, accessing network resources, and user or computer authentication. The LM authentication level determines which challenge/response authentication protocol is negotiated between the client and the server computers. Specifically, the LM authentication level determines which authentication protocols that the client will try to negotiate or that the server will accept. The value that is set for LmCompatibilityLevel determines which challenge/response authentication protocol is used for network logons. This value affects the level of authentication protocol that clients use, the level of session security negotiated, and the level of authentication accepted by servers.
       
       Possible settings include the following.

       Value	Setting	Description
       0	Send LM & NTLM responses	Clients use LM and NTLM authentication and never use NTLMv2 session security. Domain controllers accept LM, NTLM, and NTLMv2 authentication.
       1	Send LM & NTLM - use NTLMv2 session security if negotiated	Clients use LM and NTLM authentication, and use NTLMv2 session security if the server supports it. Domain controllers accept LM, NTLM, and NTLMv2 authentication.
       2	Send NTLM response only	Clients use NTLM authentication only and use NTLMv2 session security if the server supports it. Domain controllers accept LM, NTLM, and NTLMv2 authentication.
       3	Send NTLMv2 response only	Clients use NTLMv2 authentication only and use NTLMv2 session security if the server supports it. Domain controllers accept LM, NTLM, and NTLMv2 authentication.
       4	Send NTLMv2 response only/refuse LM	Clients use NTLMv2 authentication only and use NTLMv2 session security if the server supports it. Domain controllers refuse LM and accept only NTLM and NTLMv2 authentication.
       5	Send NTLMv2 response only/refuse LM & NTLM	Clients use NTLMv2 authentication only and use NTLMv2 session security if the server supports it. Domain controllers refuse LM and NTLM and accept only NTLMv2 authentication.

       Note In Windows 95, Windows 98, and Windows 98 Second Edition, the Directory Services Client uses SMB signing when it authenticates with Windows Server 2003 servers by using NTLM authentication. However, these clients do not use SMB signing when they authenticate with these servers by using NTLMv2 authentication. Additionally, Windows 2000 servers do not respond to SMB signing requests from these clients.
       
       Check the LM authentication level: You must change the policy on the server to permit NTLM, or you must configure the client computer to support NTLMv2.
       
       If the policy is set to (5) Send NTLMv2 response only\refuse LM & NTLM on the target computer that you want to connect to, you must either lower the setting on that computer or set the security to the same setting that is on the source computer that you are connecting from.
       
       Find the correct location where you can change the LAN manager authentication level to set the client and the server to the same level. After you find the policy that is setting the LAN manager authentication level, if you want to connect to and from computers that are running earlier versions of Windows, lower the value to at least (1) Send LM & NTLM - use NTLM version 2 session security if negotiated. One effect of incompatible settings is that if the server requires NTLMv2 (value 5), but the client is configured to use LM and NTLMv1 only (value 0), the user who tries authentication experiences a logon failure that has a bad password and that increments the bad password count. If account lock-out is configured, the user may eventually be locked out.
       
       For example, you may have to look on the domain controller, or you may have to examine the domain controller's policies.
       
       Look on the domain controller
       
       Note You may have to repeat the following procedure on all the domain controllers.

       1. Click Start, point to Programs, and then click Administrative Tools.

       2. Under Local Security Settings, expand Local Policies.

       3. Click Security Options.

       4. Double-click Network Security: LAN manager authentication level, and then click a value in the list.

       
       If the Effective Setting and the Local Setting are the same, the policy has been changed at this level. If the settings are different, you must check the domain controller's policy to determine whether the Network Security: LAN manager authentication level setting is defined there. If it is not defined there, examine the domain controller's policies.
       
       Examine the domain controller's policies

       1. Click Start, point to Programs, and then click Administrative Tools.

       2. In the Domain Controller Security policy, expand Security Settings, and then expand Local Policies.

       3. Click Security Options.

       4. Double-click Network Security: LAN manager authentication level, and then click a value in the list.

       
       Note

       • You may also have to check policies that are linked at the site level, the domain level, or the organizational unit (OU) level to determine where you must configure the LAN manager authentication level.

       • If you implement a Group Policy setting as the default domain policy, the policy is applied to all computers in the domain.

       • If you implement a Group Policy setting as the default domain controller's policy, the policy applies only to the servers in the domain controller's OU.

       • It is a good idea to set the LAN manager authentication level in the lowest entity of necessary scope in the policy application hierarchy.

       Windows Server 2003 has a new default setting to use NTLMv2 only. By default, Windows Server 2003 and Windows 2000 Server SP3-based domain controllers have enabled the "Microsoft network server: Digitally sign communications (always)" policy. This setting requires the SMB server to perform SMB packet signing. Changes to Windows Server 2003 were made because domain controllers, file servers, network infrastructure servers, and Web servers in any organization require different settings to maximize their security.
       
       If you want to implement NTLMv2 authentication in your network, you must make sure that all the computers in the domain are set to use this authentication level. If you apply Active Directory Client Extensions for Windows 95 or Windows 98 and Windows NT 4.0, the client extensions use the improved authentication features that are available in NTLMv2. Because client computers that are running any of the following operating system are not affected by Windows 2000 Group Policy Objects, you may have to manually configure these clients:

       • Microsoft Windows NT 4.0

       • Microsoft Windows Millennium Edition

       • Microsoft Windows 98

       • Microsoft Windows 95

       Note If you enable the Network security: Do not store LAN manager hash value on next password change policy or set the NoLMHash registry key, Windows 95-based and Windows 98-based clients that do not have the Directory Services Client installed cannot log on to the domain after a password change.
       
       Many third-party CIFS servers, such as Novell Netware 6, are not aware of NTLMv2 and use NTLM only. Therefore, levels greater than 2 do not permit connectivity. There also are third-party SMB clients that do not use extended session security. In these cases, the LmCompatiblityLevel of the resource server is not taken into consideration. The server then packs up this legacy request and sends it to the User Domain Controller. The settings on the Domain Controller then decide what hashes are used to verify the request and whether these are meeting the Domain Controller's security requirements.
       
        

       299656 How to prevent Windows from storing a LAN manager hash of your password in Active Directory and local SAM databases
        

       2701704Audit event shows authentication package as NTLMv1 instead of NTLMv2 For more information about LM authentication levels, click the following article number to view the article in the Microsoft Knowledge Base:

       239869 How to enable NTLM 2 authentication
        

    2. Risky configurations
       
       The following are harmful configuration settings:

       • Nonrestrictive settings that send passwords in cleartext and that deny NTLMv2 negotiation

       • Restrictive settings that prevent incompatible clients or domain controllers from negotiating a common authentication protocol

       • Requiring NTLMv2 authentication on member computers and domain controllers that are running versions of Windows NT 4.0 that are earlier than Service Pack 4 (SP4)

       • Requiring NTLMv2 authentication on Windows 95 clients or on Windows 98 clients that do not have the Windows Directory Services Client installed.

       • If you click to select the Require NTLMv2 session security check box in the Microsoft Management Console Group Policy Editor snap-in on a Windows Server 2003 or Windows 2000 Service Pack 3-based computer, and you lower the LAN manager authentication level to 0, the two settings conflict, and you may receive the following error message in the Secpol.msc file or the GPEdit.msc file:

         Windows cannot open the local policy database. An unknown error occurred when attempting to open the database.

         For more information about the Security Configuration and Analysis Tool, see the Windows 2000 or the Windows Server 2003 Help files.

    3. Reasons to Modify This Setting

       • You want to increase the lowest common authentication protocol that is supported by clients and domain controllers in your organization.

       • Where secure authentication is a business requirement, you want to disallow negotiation of the LM and the NTLM protocols.

    4. Reasons to disable this setting
       
       Client or server authentication requirements, or both, have been increased to the point where authentication over a common protocol cannot occur.

    5. Symbolic Name:
       
       LmCompatibilityLevel

    6. Registry Path:

       HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa\LmCompatibilityLevel

    7. Examples of compatibility problems

       • Windows Server 2003: By default, the Windows Server 2003 NTLMv2 Send NTLM responses setting is enabled. Therefore, Windows Server 2003 receives the "Access Denied" error message after the initial installation when you try to connect to a Windows NT 4.0-based cluster or to LanManager V2.1-based servers, such as OS/2 Lanserver. This issue also occurs if you try to connect from an earlier-version client to a Windows Server 2003-based server.

       • You install Windows 2000 Security Rollup Package 1 (SRP1).SRP1 forces NTLM version 2 (NTLMv2). This rollup package was released after the release of Windows 2000 Service Pack 2 (SP2).
          

       • Windows 7 and Windows Server 2008 R2: Many third-party CIFS servers, such as Novell Netware 6 or Linux-based Samba servers, are not aware of NTLMv2 and use NTLM only. Therefore, levels greater than "2" do not permit connectivity. Now in this version of the operating system, the default for LmCompatibilityLevel was changed to "3". So when you upgrade Windows, these third party filers may stop working.

       • Microsoft Outlook clients may be prompted for credentials even though they are already logged on to the domain. When users supply their credentials, they receive the following error message: Windows 7 and Windows Server 2008 R2

         The logon credentials supplied were incorrect. Make sure your username and domain are correct, then type your password again.

         When you start Outlook, you may be prompted for your credentials even if your Logon Network Security setting is set to Passthrough or to Password Authentication. After you type your correct credentials, you may receive the following error message:

         The login credentials supplied were incorrect.

         A Network Monitor trace may show that the global catalog issued a remote procedure call (RPC) fault with a status of 0x5. A status of 0x5 means "Access Denied."

       • Windows 2000: A Network Monitor capture may show the following errors in the NetBIOS over TCP/IP (NetBT) server message block (SMB) session:

         SMB R Search Directory Dos error, (5) ACCESS_DENIED (109) STATUS_LOGON_FAILURE (91) Invalid user identifier

       • Windows 2000: If a Windows 2000 domain with NTLMv2 Level 2 or later is trusted by a Windows NT 4.0 domain, Windows 2000-based member computers in the resource domain may experience authentication errors.

       • Windows 2000 and Windows XP: By default, Windows 2000 and Windows XP set the LAN Manager Authentication Level Local Security Policy option to 0. A setting of 0 means "Send LM and NTLM responses."
         
         Note Windows NT 4.0-based clusters must use LM for administration.

       • Windows 2000: Windows 2000 clustering does not authenticate a joining node if both nodes are part of a Windows NT 4.0 Service Pack 6a (SP6a) domain.

       • The IIS Lockdown Tool (HiSecWeb) sets the LMCompatibilityLevel value to 5 and the RestrictAnonymous value to 2.

       • Services for Macintosh
         
         User Authentication Module (UAM): The Microsoft UAM (User Authentication Module) provides a method for encrypting the passwords that you use to log on to Windows AFP (AppleTalk Filing Protocol) servers. The Apple User Authentication Module (UAM) provides only minimal or no encryption. Therefore, your password could easily be intercepted on the LAN or on the Internet. Although the UAM is not required, it does provide encrypted authentication to Windows 2000 Servers that run Services For Macintosh. This version includes support for NTLMv2 128-bit encrypted authentication and a MacOS X 10.1-compatible release.
         
         By default, the Windows Server 2003 Services for Macintosh server permits only Microsoft Authentication.
          

       • Windows Server 2008, Windows Server 2003, Windows XP, and Windows 2000: If you configure the LMCompatibilityLevel value to be 0 or 1 and then configure the NoLMHash value to be 1, applications and components may be denied access through NTLM. This issue occurs because the computer is configured to enable LM but not to use LM-stored passwords.
         
         If you configure the NoLMHash value to be 1, you must configure the LMCompatibilityLevel value to be 2 or higher.

11. Network security: LDAP client signing requirements

    1. Background
       
       The Network security: LDAP client signing requirements setting determines the level of data signing that is requested on behalf of clients that issue Lightweight Directory Access Protocol (LDAP) BIND requests as follows:

       • None: The LDAP BIND request is issued with the caller-specified options.

       • Negotiate signing: If the Secure Sockets Layer/Transport Layer Security (SSL/TLS) has not been started, the LDAP BIND request is initiated with the LDAP data signing option set in addition to the caller-specified options. If SSL/TLS has been started, the LDAP BIND request is initiated with the caller-specified options.

       • Require signing: This is the same as Negotiate signing. However, if the LDAP server's intermediate saslBindInProgress response does not indicate that LDAP traffic signing is required, the caller is told that the LDAP BIND command request failed.

    2. Risky configuration
       
       Enabling the Network security: LDAP client signing requirements setting is a harmful configuration setting. If you set the server to require LDAP signatures, you must also configure LDAP signing on the client. Not configuring the client to use LDAP signatures will prevent communication with the server. This causes user authentication, Group Policy settings, logon scripts, and other features to fail.

    3. Reasons to Modify This Setting
       
       Unsigned network traffic is susceptible to man-in-the-middle attacks where an intruder captures packets between the client and the servers, modifies them, and then forwards them to the server. When this occurs on an LDAP server, an attacker could cause a server to respond based on false queries from the LDAP client. You can lower this risk in a corporate network by implementing strong physical security measures to help protect the network infrastructure. Additionally, you can help prevent all kinds of man-in-the-middle attacks by requiring digital signatures on all network packets by means of IPSec authentication headers.

    4. Symbolic Name:
       
       LDAPClientIntegrity

    5. Registry Path:

       HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LDAP\LDAPClientIntegrity

12. Event Log: Maximum security log size

    1. Background
       
       The Event Log: Maximum security log size security setting specifies the maximum size of the security event log. This log has a maximum size of 4 GB. To locate this setting, expand
       Windows Settings, and then expand Security Settings.

    2. Risky configurations
       
       The following are harmful configuration settings:

       • Restricting the security log size and the security log retention method when the Audit: Shut down system immediately if unable to log security audits setting is enabled. See the "Audit: Shut down system immediately if unable to log security audits" section of this article for more details.

       • Restricting the security log size so that security events of interest are overwritten.

    3. Reasons to Increase This Setting
       
       Business and security requirements may dictate that you increase the security log size to handle additional security log detail or to retain security logs for a longer period of time.

    4. Reasons to Decrease This Setting
       
       Event Viewer logs are memory mapped files. The maximum size of an event log is constrained by the amount of physical memory in the local computer and by the virtual memory that is available to the event log process. Increasing the log size beyond the amount of virtual memory that is available to Event Viewer does not increase the number of log entries that are maintained.

    5. Examples of compatibility problems
       
       Windows 2000: Computers that are running versions of Windows 2000 that are earlier than Service Pack 4 (SP4) may stop logging events in the event log before reaching the size that is specified in the Maximum log size setting in Event Viewer if the Do not overwrite events (clear log manually) option is turned on.
       
       
        

13. Event Log: Retain security log

    1. Background
       
       The Event Log: Retain security log security setting determines the "wrapping" method for the security log. To locate this setting, expand Windows Settings, and then expand Security Settings.

    2. Risky configurations
       
       The following are harmful configuration settings:

       • Failing to retain all logged security events before they are overwritten

       • Configuring the Maximum security log size setting too small so that security events are overwritten

       • Restricting the security log size and retention method while the Audit: Shut down system immediately if unable to log security audits security setting is enabled

    3. Reasons to enable this setting
       
       Enable this setting only if you select the Overwrite events by days retention method. If you use an event correlation system that polls for events, make sure that the number of days is at least three times the poll frequency. Do this to allow for failed poll cycles.

14. Network access: Let Everyone permissions apply to anonymous users

    1. Background
       
       By default, the Network access: Let Everyone permissions apply to anonymous users setting is set to Not Defined on Windows Server 2003. By default, Windows Server 2003 does not include the Anonymous Access token in the Everyone group.

    2. Example of Compatibility Problems
       
       The following value of

       HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\LSA\everyoneincludesanonymous [REG_DWORD]=0x0 breaks trust creation between Windows Server 2003 and Windows NT 4.0, when the Windows Server 2003 domain is the account domain and the Windows NT 4.0 domain is the resource domain. This means that the account domain is Trusted on Windows NT 4.0 and the resource domain is Trusting on the Windows Server 2003 side. This behavior occurs because the process to start the trust after the initial anonymous connection is ACL'd with the Everyone token that includes the Anonymous SID on Windows NT 4.0.

    3. Reasons to Modify This Setting
       
       The value must be set to 0x1 or set by using a GPO on the domain controller's OU to be: Network access: Let Everyone permissions apply to anonymous users - Enabled to make the trust creations possible.
       
       Note Most other security settings go up in value instead of down to 0x0 in their most secured state. A more secure practice would be to change the registry on the primary domain controller emulator instead of on all the domain controllers. If the primary domain controller emulator role is moved for any reason, the registry must be updated on the new server.
       
       A restart is required after this value is set.

    4. Registry Path

       HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\LSA\everyoneincludesanonymous

15. NTLMv2 authentication

    1. Session security
       
       Session security determines the minimum security standards for client and server sessions. It is a good idea to verify the following security policy settings in the Microsoft Management Console Group Policy Editor snap-in:

       • Computer Settings\Windows Settings\Security Settings\Local Policies\Security Options

       • Network Security: Minimum session security for NTLM SSP based (including secure RPC) servers

       • Network Security: Minimum session security for NTLM SSP based (including secure RPC) clients

       The options for these settings are as follows:

       • Require message integrity

       • Require message confidentiality

       • Require NTLM version 2 session security

       • Require 128-bit encryption

       The default setting prior to Windows 7 is No requirements. Starting with Windows 7, the default changed to Require 128-bit encryption for improved security. With this default, legacy devices that don’t support 128-bit encryption will be unable to connect.
       
       These policies determine the minimum security standards for an application-to-application communications session on a server for a client.
       
       Note that although described as valid settings, the flags to require message integrity and confidentiality are not used when the NTLM session security is determined.
       
       Historically, Windows NT has supported the following two variants of challenge/response authentication for network logons:

       • LM challenge/response

       • NTLM version 1 challenge/response

       LM allows interoperability with the installed base of clients and servers. NTLM provides improved security for connections between clients and servers.
       
       The corresponding registry keys are as follows:

       HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa\MSV1_0\"NtlmMinServerSec"
       HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa\MSV1_0\"NtlmMinClientSec"

    2. Risky configurations
       
       This setting controls how network sessions secured using NTLM will be handled. This affects RPC-based sessions authenticated with NTLM, for example. There are the following risks:

       • Using older authentication methods than NTLMv2 makes the communication easier to attack due to the simpler hashing methods used.

       • Using encryption keys lower than 128-bit allows attackers to break communication using brute-force attacks.

Time synchronization

Time synchronization failed. The time is off by more than 30 minutes on an affected computer. Make sure that the client computer's clock is synchronized with the domain controller's clock.

Workaround for SMB signing

We recommend that you install Service Pack 6a (SP6a) on Windows NT 4.0 clients that interoperate in a Windows Server 2003-based domain. Windows 98 Second Edition-based clients, Windows 98-based clients, and Windows 95-based clients must run the Directory Services Client to perform NTLMv2. If Windows NT 4.0-based clients do not have Windows NT 4.0 SP6 installed or if Windows 95-based clients, Windows 98-based clients, and Windows 98SE-based clients do not have the Directory Services Client installed, disable SMB signing in the default domain controller's policy setting on the domain controller's OU, and then link this policy to all OUs that host domain controllers.

The Directory Services Client for Windows 98 Second Edition, Windows 98, and Windows 95 will perform SMB Signing with Windows 2003 servers under NTLM authentication, but not under NTLMv2 authentication. Additionally, Windows 2000 servers will not respond to SMB Signing requests from these clients.

Although we do not recommend it, you can prevent SMB signing from being required on all domain controllers that run Windows Server 2003 in a domain. To configure this security setting, follow these steps:

1. Open the default domain controller's policy.

2. Open the Computer Configuration\Windows Settings\Security Settings\Local Policies\Security Options folder.

3. Locate and then click the Microsoft network server: Digitally sign communications (always) policy setting, and then click Disabled.

Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:

322756 How to back up and restore the registry in Windows Alternatively, turn off SMB signing on the server by modifying the registry. To do this, follow these steps:

1. Click Start, click Run, type regedit, and then click OK.

2. Locate and then click the following subkey:
   HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Lanmanserver\Parameters

3. Click the enablesecuritysignature entry.

4. On the Edit menu, click Modify.

5. In the Value data box, type 0, and then click OK.

6. Exit Registry Editor.

7. Restart the computer, or stop and then restart the Server service. To do this, type the following commands at a command prompt, and then press Enter after you type each command:
   net stop server
   net start server

Note The corresponding key on the client computer is in the following registry subkey:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Lanmanworkstation\Parameters The following lists the translated error code numbers to status codes and to the verbatim error messages that are mentioned earlier:

For more information, click the following article numbers to view the articles in the Microsoft Knowledge Base:

324802 How to configure Group Policies to set security for system services in Windows Server 2003

816585 How to apply predefined security templates in Windows Server 2003