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This chapter is from the book

This chapter is from the book

Authentication Policies

A number of specific settings can be applied through policies defined either locally, across a number of computers, or domainwide. Local policies on a single computer are configured with the Local Security Policy tool. Settings that are to be applied to a number of computers are configured with the Group Policy tool, and templates can be used to make configuration of a number of options easier. Domain account policies are defined in the Domain Group Policy. Account policies were discussed earlier in this chapter, so this section provides an overview of the authentication policy options that are available for the Windows XP network administrator in a nondomain environment. To modify any of these policies:

  1. Launch Control Panel, then select Administrative Tools, then select Local Security Policy.

  2. In the left-hand pane of the console select Local Policies, and then select the appropriate folder for the option you wish to modify.

  3. In the right-hand pane, right-click the policy you wish to modify and select Properties from the pop-up menu. The property sheet for that policy appears. Make changes as appropriate for the policy you are configuring.

User Rights Assignment

User rights pertain to the specific activities that users may perform, such as loading or unloading device drivers, limiting access to specific computers, or changing the system time. These rights can be assigned to a user or a group; Microsoft's stance is and always has been that it is better to set permissions and rights by group, rather than by individual users. If you only have a handful of users in your network, management by group may be more difficult than administering each user independently. However, if you have more than 10 to15 users, group management is usually easier in the long run. Regardless of whether you manage by users or groups, assigning rights uses the same process: Double-click the policy option under the User Rights assignment folder, click the Add User or Group button, and supply the appropriate user or group name(s).

The following user rights deal with authentication-related issues.

  • Access this computer from the network: Permits a user to connect to a specific computer via network.

  • Deny access to this computer from the network: Prohibits a remote user or group from accessing a specific computer from the network. Useful for securing servers with large numbers of directories that should not be accessed by anyone other than a specific group or user.

  • Allow logon through Terminal Services: Users are permitted to connect to the computer via terminal services.

  • Deny logon through Terminal Services: Disables terminal service access to specific users or groups, while still allowing those with "Allow logon through Terminal Services" rights to continue doing so.

  • Log on as a batch job: Allows a user, such as a service account, to log on by means of a batch job.

  • Deny logon as a batch job: Prevents specific users and groups from logging on as a batch.

  • Log on as a service: Enables accounts to log on as a service, in order to access resources on behalf of an application.

  • Deny logon as a service: Prevents specific users and groups from logging on as a service.

  • Log on locally: Permits users to use this computer locally.

  • Deny logon locally: Prohibits specific users or groups from using the computer locally. Useful in instances where a computer is in a public area but you want to limit the use to a specific user or two.

Security Options

Security Options govern specific configuration options that are used to increase or decrease security on a given computer. These options are assigned to the computer, not users or groups, unlike User Rights Assignment. All users of this computer are subject to these policies. The following Security Options deal with authentication-related issues and are located in the Security Options folder under Local Security Policy. To modify a policy, double-click it and make the necessary changes.

  • Do not display last user name: Hides the last username in the Control + Alt + Delete log-on screen. This makes it difficult for fraudulent users to access your network by guessing passwords based on known usernames.

  • Do not require CTRL+ALT+DEL: Eliminates the need to press Control + Alt + Delete to log on. This puts the user credentials at risk, as the MSGINA is no longer able to use a secure channel to transmit credentials, and a fraudulent user can capture the password, even without sending data over a network.

  • Message text for users attempting to log on: You can specify a legal warning or disclaimer that appears before users are permitted to log on.

  • Message title for users attempting to log on: This controls the title of the window where pre-log-on messages appear. Title suggestions include Warning, Notice, and Attention.

  • Number of previous logons to cache (in case a domain controller is not available): Sets the number of log-on attempts to be stored by a domain account. This is helpful for remote computers where an Internet connection must be made before a domain controller can be contacted. If the ISP has unreliable service, a domain user can be locked out if the connection cannot be made. The downside of this is that a fraudulent user can disconnect a computer from the network and use recently changed credentials to log in to the network without being blocked by a domain controller. Zero disables caching.

  • Prompt user to change password before expiration: Gives users a warning that they will be required to change account passwords in the near future.

  • Require domain controller authentication to unlock: Prevents a user from using cached credentials to log on to a computer that has been locked.

  • Smart card removal behavior: If smart cards are used, you can determine what will happen if a card is removed while the computer is in use. The choices are Lock workstation, Force Log off, and No action.

  • Allow anonymous SID/Name translation: Enables anonymous users to translate SIDs into usernames and vice versa.

  • Do not allow anonymous enumeration of SAM accounts: Prohibits anonymous users from enumerating the SAM.

  • Do not allow Stored User Names and Passwords to save passports or credentials for domain authentication: Prevents passport or domain authentication credentials from being saved after user has logged off, if Saved Passwords has been configured.

  • Sharing and security model for local accounts: Guest only requires all network logons to use the Guest account. Classic allows network users to use their own credentials.

  • Let Everyone permissions apply to Anonymous users: Grants Everyone group permissions to anonymous users.

  • Do not store LAN Manager hash value on next password change: LAN Manager hash is deleted after a password change.

  • Force log off when log-on time expires: Requires a user to be forcefully logged off the computer if a time constraint has been placed on his or her account. The account equivalent of Cinderella's carriage becoming a pumpkin at midnight.

  • LAN Manager Authentication Level: Sets LAN Manager authentication requirements for networks with down-level Windows hosts.

  • Minimum session security for NTLM SSP based (including secure RPC) clients: Permits configuration of the following options:

    • Require message integrity

    • Require message confidentiality

    • Require NTLMv2 session security

    • Require 128-bit encryption

  • Allow system to be shut down without having to log on: Permits or prohibits a computer from being shut down without the user being logged on.

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