MCTS 70-640 Exam Cram: Group Policy and Active Directory Security

This chapter is from the book 

Terms You’ll Need to Understand
	Account lockout
	Account policies
	Auditing
	Auditpol.exe
	Fine-grained password policies
	Password settings objects (PSO)

Concepts/Techniques You’ll Need to Master
	Managing security configurations
	Configuring account policies
	Configuring fine-grained password policies
	Using Group Policy to configure auditing policies
	Using Auditpol.exe to configure auditing policies

You have seen how Group Policy works and how to set up Group Policy objects (GPO) to configure various aspects of the Windows computing environment. You have also learned about Group Policy succession and how you can modify the sequence in which GPOs are applied and its effect when policy settings conflict with one another. You have also read about the use of Group Policy to maintain a consistent software environment, where users and computers receive a well-regulated set of software applications that can be modified and upgraded as required, as well as the removal of outdated software. This chapter focuses on the use of Group Policy to create and enforce a secure computing environment that protects your computers and data from whatever the bad guys might attempt to throw at you.

Use of Group Policy to Configure Security

You can use Group Policy to manage security settings quite effectively on a Windows Server 2008 network. An enhanced range of security options is available, with settings designed for both user and computer configuration. Microsoft continues to expand the available range of security policies, compared to those included with previous versions of Windows Server. The most significant addition to security settings in Windows Server 2008 is that of fine-grained password policies, which enable you to set different password policies for different portions of your AD DS domain.

Group Policy in Windows Server 2008 includes a large range of security options designed for both user and computer configuration. As you can see in Figure 7.1, most of these security settings are applied to the Computer Configuration section in the Group Policy Management Editor. This section is mainly concerned with account policies.

Configuring Account Policies

The Account Policies node contains settings related to user accounts, including the password policy, account lockout policy, and Kerberos policy. Before looking at the new Windows Server 2008 feature of fine-grained password policies, this section examines these policies and how to configure them, in general. It briefly introduces each of these concepts in the following sections.

Domain Password Policies

You can use domain-based Group Policy to configure password policy settings that help to protect users of Windows 2000/XP/Vista client computers. The options available in Windows Server 2008 are similar to those introduced in Windows 2000 and continued in Windows Server 2003. Password policies are generally intended to make passwords more difficult for intruders to discover. Figure 7.2 shows the available password policies and their default settings.

The following password policy settings are available:

• Enforce Password History—Determines the number of passwords remembered by AD DS for each user. Values range from 0 to 24. A user cannot reuse a password retained in the history list. A value of 0 means that no password history is retained and a user can reuse passwords at will. Windows Server 2008 continues with the default of 24 established with Windows Server 2003 SP1.

• Maximum Password Age—Determines the number of days that a user can use a password before being required to specify a new one. Values range from 0 to 999. A value of 0 means that a user is never required to change his password. The default is 90 days.

• Minimum Password Age—Determines the minimum number of days a password must be used before it can be changed. Values range from 0 to 999 days and must be less than the maximum password age. A value of 0 allows the user to immediately change a new password. This value would allow a user to cycle through an entire history list of passwords in a short time—in other words, repeatedly changing a password so he could reuse his old password. This obviously defeats the purpose of enforcing password history. The default is 1 day.

• Minimum Password Length—Determines the minimum number of characters that can make up a password. Values range from 0 to 14. A value of 0 permits a blank password. Use a setting of 10 or higher for increased security. The default is 7 characters.

• Password Must Meet Complexity Requirements—Stipulates that a password must meet complexity criteria, as follows: The password cannot contain the user account name or full name, or parts of the name that exceed two consecutive characters. It must contain at least three of the following four items:

  • English lowercase letters
  • English uppercase letters
  • Numerals
  • Nonalphanumeric characters, such as $ ; [ ] { } ! .

• Store Passwords Using Reversible Encryption—Determines the level of encryption used by Windows Server 2008 for storing passwords. Enabling this option reduces security because it stores passwords in a format that is essentially the same as plain text. This option is disabled by default. You should enable this policy only if needed for clients who cannot use normal encryption, such as those using Challenge Handshake Authentication Protocol (CHAP) authentication or Internet Information Services (IIS) Digest Authentication.

To configure these policies, expand the Computer Configuration node of the appropriate GPO, as shown in Figure 7.2. Right-click the desired policy and choose Properties. Then configure the appropriate value and click OK. Each policy setting also has an Explain tab that provides additional information on the policy setting and its purpose.

Account Lockout

A cracked user account password jeopardizes the security of the entire network. The account lockout policy is designed to lock an account out of the computer if a user (or intruder attempting to crack the network) enters an incorrect password a specified number of times, thereby limiting the effectiveness of dictionary-based password crackers. The account lockout policy contains the following settings:

• Account Lockout Duration—Specifies the number of minutes that an account remains locked out. Every account except for the default Administrator account can be locked out in this manner. You can set this value from 0 to 99999 minutes, or about 69.4 days. A value of 0 means that accounts that have exceeded the specified number of failed logon attempts are locked out indefinitely until an administrator unlocks the account.

• Account Lockout Threshold—Specifies the number of failed logon attempts that can occur before the account is locked out. You can set this value from 0 to 999 failed attempts. A value of 0 means that the account will never be locked out. Best practices recommend that you should never configure a setting of 0 here.

• Reset Account Lockout Counter After—Specifies the number of minutes to wait after which the account lockout counter is reset to 0. You can set this value from 1 to 99999.

When you configure this policy, Windows Server 2008 sets default values for the account lockout settings. To configure an account lockout policy, right-click any of the three values and choose Properties, and then accept the default provided or specify a value of your choice. As shown in Figure 7.3, Windows suggests default values for the other two policy settings. Click OK to define the policy settings and set these defaults. If you want to change the other settings, right-click the appropriate settings and choose Properties, and then enter the desired value.

Unlocking an Account

When a user account is locked out because of too many incorrect attempts at entering a password, it is simple for an administrator or user who is delegated the task to unlock it. Right-click the user account in Active Directory Users and Computers and choose Properties. On the Account tab of the user’s Properties dialog box, the Unlock Account check box should display a message stating This account is currently locked out on this Active Directory Domain Controller. Select the check box, and then click OK or Apply.

Kerberos Policy

The Kerberos Policy subnode contains settings that enforce use logon restrictions according to validation requests made to the Kerberos Key Distribution Center (KDC) against the user rights policy of the user account. By default, the policies in this section are enabled. They define the maximum lifetime for user and service tickets as well as the maximum tolerance for computer clock synchronization.

Fine-Grained Password Policies

Active Directory domains in Windows 2000 and Windows Server 2003 permitted only a single password and account lockout policy, defined at the domain level. If an organization wanted different password policy settings for a specified group of users, an administrator had to create a new domain or use a third-party custom password filter. Windows Server 2008 introduces the concept of fine-grained password policies, which enable you to apply granular password and account lockout policy settings to different sets of users within the same domain. For example, you can apply stricter policy settings to accounts associated with users who have access to classified or restricted information, such as legal and product research departments. At the same time, you can maintain more relaxed settings for accounts of other users where these types of information are not available.

To configure a fine-grained password policy, you must be a member of the Domain Admins group, and the domain functional level must be set to Windows Server 2008. You can also delegate control of the task to other users if required.

Fine-grained password policies are stored in AD DS by means of two new object classes that are defined in the schema:

• Password Settings Container—Created by default under the domain’s System container, the Password Settings Container stores the password settings objects (PSO) for the domain.

• Password Settings Object—Holds attributes for all the password policy and account lockout policy settings, as defined earlier in this section. It also contains a multivalued link attribute that links the PSO to users or groups, and an integer precedence value that resolves conflicts if multiple PSOs are applied to the same user or group.

You can link a PSO to a user, global security group, or InetOrgPerson object that is in the same domain. Note that if you link a PSO to a distribution group or a group with a different scope, the PSO is ignored. If multiple PSOs are linked to a single user or group because of membership in multiple groups, only one PSO can be applied; settings cannot be merged between PSOs.

Password Settings Precedence

If more than one PSO is linked to a user or group, the PSO that applies is determined by the precedence attribute, which is associated with each PSO and has an integer value of 1 or greater. The lower the precedence attribute, the higher the priority of a given PSO; for example, a PSO with a precedence value of 3 overrides another PSO with a precedence value of 5.

The following rules determine the resultant PSO that is applied to a user or group when multiple PSOs are present:

• If a PSO is directly linked to the user object, it prevails. Should more than one PSO be linked directly to the user, the PSO with the lowest precedence value prevails, and a warning message is logged to the event log.
• If no PSO is linked directly to the user object, all PSOs applied to the user according to membership in global security groups are evaluated, and the PSO with the lowest precedence value prevails. If more than one PSO with the same precedence value is present, the PSO that is obtained first is used.
• If no PSO is linked to either the user object or any global security groups it is a member of, the settings in the Default Domain Policy GPO are applied.

Configuring Fine-Grained Password Policies

As already stated, you must be a member of the Domain Admins group to create and manage PSOs. You can use the ADSI Edit utility to configure a fine-grained password policy. This involves specifying values for all the Password Policy and Account Lockout Policy settings described earlier in this chapter. This tool was introduced in Chapter 4, “Configuring Additional Active Directory Roles.” Perform the following steps:

1. Click Start, Run, type adsiedit.msc, and then press Enter.
2. If the domain name is not visible in the console tree, right-click ADSI Edit and choose Connect To. If Default Naming Context and your domain name are visible in the Connection Settings dialog box, accept them. Otherwise, type the fully qualified domain name (FQDN) of your domain. Then click OK.
3. Expand your domain name to locate the CN=System container, and then expand this container to locate the CN=Password Settings Container object.
4. Select this container to display any PSOs that are configured in the domain in the Details pane.
5. Right-click this container and choose New, Object. This starts a wizard that enables you to define your PSO.
6. In the Create Object dialog box, the msDS-PasswordSettings object class is the only available class. Ensure that it is selected, and then click Next.
7. Provide a descriptive value for your PSO, as shown in Figure 7.4, and then click Next.
   

   Figure 7.4 Provide a descriptive value that helps you to identify the PSO later.

8. Type a value for the Password Settings Precedence, and then click Next.
9. For Password Reversible Encryption Status for User Accounts, type False unless you need reversible encryption, and then click Next.
10. Type a value for the password history length, and then click Next.
11. To require password complexity, type True, and then click Next.
12. Specify a minimum password length, and then click Next.
13. For the Minimum Password Age for User Accounts value, type a value in the format days:hours:minutes:seconds (for example, 1:00:00:00), and then click Next.
14. Type a value for Maximum Password Age for User Accounts in the same format, and then click Next.
15. Type a value for the lockout threshold (number of incorrect passwords before account locks out), and then click Next.
16. Type a value for the lockout observation window (time for resetting lockout counter) in the same format as already described (for example, 00:00:30:00 for 30 minutes), and then click Next.
17. Type a value for the lockout duration in the same format, and then click Next.
18. If you want to define additional optional attributes, click More Attributes. Otherwise, click Finish to complete the creation of the PSO.

To apply the PSO to a user or group, proceed as follows:

1. Open Active Directory Users and Computers and select Advanced Features under the View menu.
2. In the console tree, expand System, and then select Password Settings Container. This displays the PSO in the Details pane.
3. Right-click the PSO and choose Properties.
4. Select the Attribute Editor tab. As shown in Figure 7.5, this tab displays the values of all attributes that have been configured for the PSO, including those set when you created the PSO.
   

   Figure 7.5 The Attribute Editor tab of the PSO’s Properties dialog box includes the values of the password and lockout attributes that you configured.

5. Scroll to select the msDS-PSOAppliesTo attribute, and then click Edit.
6. On the Multi-valued Distinguished Name With Security Principal Editor dialog box that displays, click Add Windows Account, type the user or group name, and then click OK. As shown in Figure 7.6, the name you added is displayed in this dialog box. You can also add a user or group with its LDAP distinguished name (DN) by clicking the Add DN button.
   

   Figure 7.6 Specifying a user or group that will receive the password policy.

7. Click OK. The security identifier (SID) of the user or group appears in the Value column of the Attribute Editor tab. You can repeat this process as many times as needed to link the PSO to additional users or groups.
8. Click OK to close the PSO’s Properties dialog box.

Managing Fine-Grained Password Policies

You can perform several additional managerial tasks on your PSO, as follows:

• Editing policy settings—As described in the previous section, access the Attribute Editor tab of the PSO’s Properties dialog box. Select the policy setting to be edited and click Edit. Then specify the desired value in the Editor dialog box that appears.

• Modify the PSO’s precedence value—In the Attribute Editor tab of the PSO’s Properties dialog box, select the msDS-PasswordSettingsPrecedence value, click Edit, and then specify the desired value in the Integer Attribute Editor dialog box that appears.

• Delete the PSO—If you no longer need the PSO, select it in the Details pane of Active Directory Users and Computers and press the Delete key (or right-click it and choose Delete). Click Yes in the confirmation message box that appears. The policy settings for any users or groups employing this PSO revert to the settings in a lower-priority PSO or to the Default Domain Policy GPO if no other PSO exists.

Viewing the Resultant PSO

As already stated, a PSO configured for the user takes priority over one that is configured for a group to which the user belongs, and group-based PSOs are applied according to the precedence value. If you have configured a large number of PSOs, troubleshooting their application can become problematic. To facilitate this process, you can view which PSO is applying to a user or group. Proceed as follows:

1. In Active Directory Users and Computers, ensure that Advanced Features is selected.
2. Select the Users container or the OU of the desired user account to display the user account in the Details pane.
3. Right-click the user account and choose Properties.
4. Select the Attribute Editor tab, and then click Filter. In the options list that appears, ensure that Show Attributes/Optional and Show Read-Only Attributes/System-Only are checked.
5. Scroll the attribute list to locate msDS-ResultantPSO. The value of this attribute displays the DN of the effective PSO, as shown in Figure 7.7. If it displays <not set>, the password settings in the Default Domain Policy GPO are in effect for this account. Click View to see the complete DN.

For additional information on fine-grained password policies, including some recommended scenarios for applying these policies, refer to “Step-by-Step Guide for Fine-Grained Password and Account Lockout Policy Configuration” in Appendix A. Links in this appendix also provide additional information on the available attributes and their permitted values.

Security Options

Besides account policies, the Security Settings subnode of Computer Configuration includes a large range of additional security-related policy settings. These settings are summarized here:

• Local Policies—Includes audit policies, discussed later in this chapter, and user rights assignment, discussed in Chapter 6, “Configuring and Troubleshooting Group Policy.” The Security Options subnode within this node includes a large set of policy options, as shown in Figure 7.8, that are important in controlling security aspects of the computers to which the GPO applies. Several of the more important options that you should be familiar with are as follows:

  • Accounts: Rename Administrator Account—This option renames the default administrator account to a value you specify. Intruders cannot simply look for “Administrator” when attempting to crack your network.

  • Interactive Logon: Do Not Display Last User Name—Enable this option to prevent the username of the last logged-on user from appearing in the Logon dialog box, thus preventing another individual from seeing a username. This can also reduce lockouts.

  • Interactive Logon: Do Not Require CTRL+ALT+DEL—When enabled, a user is not required to press Ctrl+Alt+Delete to obtain the Logon dialog box. Disable this policy in a secure environment to require the use of this key combination. Its use prevents rogue programs such as Trojan horses from capturing usernames and passwords.

  • Interactive Logon: Require Smart Card—When enabled, users must employ a smart card to log on to the computer.

  • User Account Control—Several policy settings determine the behavior of the UAC prompt for administrative and nonadministrative users, including behavior by applications that are in secure locations on the computer, such as %ProgramFiles% or %Windir%.

  

  Figure 7.8 You can configure numerous local security policy settings with Group Policy in Windows Server 2008.

  For more information on the policy settings in this node, refer to “Domain Controller and Member Server Policy Settings” in Appendix A.

• Event Log—Configuration options for the Event Viewer logs, including log sizes and action taken when an event log is full.

• Restricted Groups—Determines who can belong to certain groups, as discussed in Chapter 6.

• System Services—Enables you to configure system services properties, such as startup type, and restrict users from modifying these settings.

• Registry—Enables you to control the permissions that govern who can access and edit portions of the Registry.

• File System—Enables you to configure permissions on folders and files and prevent their modification.

• Wired Network (IEEE 802.3) Policies—Enables you to specify the use of IEEE 802.1X authentication for network access by Windows Vista computers, including the protocol to be used for network authentication.

• Windows Firewall with Advanced Security—Enables you to configure properties of Windows Firewall for domain, private, and public profiles. You can specify inbound and outbound connection rules as well as monitoring settings.

• Network List Manager Policies—Enables you to control the networks that computers can access and their location types, such as public and private (which automatically specifies the appropriate firewall settings according to location type). You can also specify which networks a user is allowed to connect to.

• Wireless Network (IEEE 802.11) Policies—Enables you to specify wireless settings, such as enabling 802.1X authentication and the preferred wireless networks that users can access.

• Public Key Policies—Enables you to configure public key infrastructure (PKI) settings. Chapter 9, “Active Directory Certificate Services,” discusses several of these policies.

• Software Restriction Policies—Enables you to specify which software programs users can run on network computers, which programs users on multiuser computers can run, and the execution of email attachments. You can also specify whether software restriction policies apply to certain groups such as administrators.

• Network Access Protection—Network Access Protection (NAP) is a new Windows Server 2008 feature that enables you to define client health policies that restrict access to your network by computers that lack appropriate security configurations. The NAP policies enable you to specify settings for client user interface items, trusted servers, and servers used for enforcement of client computer security health status.

• IP Security Policies on Active Directory—Controls the implementation of IP Security (IPSec) as used by the computer for encrypting communications over the network.

You can obtain additional information on many of these policy settings in the Windows Server 2008 Help and Support and from “Security Settings Overview for GPMC” in Appendix A.

Additional Security Configuration Tools

Windows Server 2008 includes the following additional tools that are useful in configuring and maintaining the security of your AD DS network:

• Security Configuration Wizard—This wizard assists you in maintaining the security of your servers and checks for vulnerabilities that might appear as server configurations change over time. It is particularly useful in maintaining the security of servers hosting roles that are not installed using Server Manager, such as SQL Server and Exchange Server, as well as servers that host non-Microsoft applications. Microsoft also includes a command-line version, scwcmd.exe, which is useful in configuring Server Core computers.

• Security Templates snap-in—From this snap-in, you can save a custom security policy that includes settings from the various subnodes of the Security Settings node of Computer Configuration discussed in the preceding settings. It is most useful in defining a security configuration for standalone servers that are not members of a domain.

• Security Configuration and Analysis snap-in—This snap-in enables you to analyze and configure local computer security. You can compare security settings on the computer to those in a database created from the Security Templates snap-in and view any differences that you find. You can then use this database to configure the computer’s security so that it matches the database settings.

These security tools are most useful in situations involving standalone computers and servers running custom applications and are not emphasized on Exam 70-640. For more information on these tools, refer to “Server Security Policy Management in Windows Server 2008” in Appendix A.