Group Policy is a feature of the Microsoft Windows NT family of operating systems that controls the working environment of user accounts and computer accounts. Group Policy provides centralized management and configuration of operating systems, applications, and users' settings in an Active Directory environment. A version of Group Policy called Local Group Policy ("LGPO" or "LocalGPO") also allows Group Policy Object management on standalone and non-domain computers.
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Operation
Group Policy, in part, controls what users can and cannot do on a computer system: for example, to enforce a password complexity policy that prevents users from choosing an overly simple password, to allow or prevent unidentified users from remote computers to connect to a network share, to block access to the Windows Task Manager or to restrict access to certain folders. A set of such configurations is called a Group Policy Object (GPO).
As part of Microsoft's IntelliMirror technologies, Group Policy aims to reduce the cost of supporting users. IntelliMirror technologies relate to the management of disconnected machines or roaming users and include roaming user profiles, folder redirection, and offline files.
Enforcement
To accomplish the goal of central management of a group of computers, machines should receive and enforce GPOs. A GPO that resides on a single machine only applies to that computer. To apply a GPO to a group of computers, Group Policy relies on Active Directory (or on third-party products like ZENworks Desktop Management) for distribution. Active Directory can distribute GPOs to computers which belong to a Windows domain.
By default, Microsoft Windows refreshes its policy settings every 90 minutes with a random 30 minutes offset. On Domain controllers, Microsoft Windows does so every five minutes. During the refresh, it discovers, fetches and applies all GPOs that apply to the machine and to logged-on users. Some settings - such as those for automated software installation, drive mappings, startup scripts or logon scripts - only apply during startup or user logon. Since Windows XP, users can manually initiate a refresh of the group policy by using the gpupdate command from a command prompt.
Group Policy Objects are processed in the following order (from top to bottom):
- Local - Any settings in the computer's local policy. Prior to Windows Vista, there was only one local group policy stored per computer. Windows Vista and later Windows versions allow individual group policies per user accounts.
- Site - Any Group Policies associated with the Active Directory site in which the computer resides. (An Active Directory site is a logical grouping of computers, intended to facilitate management of those computers based on their physical proximity.) If multiple policies are linked to a site, they are processed in the order set by the administrator.
- Domain - Any Group Policies associated with the Windows domain in which the computer resides. If multiple policies are linked to a domain, they are processed in the order set by the administrator.
- Organizational Unit - Group policies assigned to the Active Directory organizational unit (OU) in which the computer or user are placed. (OUs are logical units that help organizing and managing a group of users, computers or other Active Directory objects.) If multiple policies are linked to an OU, they are processed in the order set by the administrator.
The resulting Group Policy settings applied to a given computer or user are known as the Resultant Set of Policy (RSoP). RSoP information may be displayed for both computers and users using the gpresult command.
Inheritance
A policy setting inside a hierarchical structure is ordinarily passed from parent to children, and from children to grandchildren, and so forth. This is termed inheritance. It can be blocked or enforced to control what policies are applied at each level. If a higher level administrator (enterprise administrator) creates a policy that has inheritance blocked by a lower level administrator (domain administrator), this policy will still be processed.
Where a Group Policy Preference Settings is configured and there is also an equivalent Group Policy Setting configured, then the value of the Group Policy Setting will take precedence.
Filtering
WMI filtering is the process of customizing the scope of the GPO by choosing a Windows Management Instrumentation (WMI) filter to apply. These filters allow administrators to apply the GPO only to, for example, computers of specific models, RAM, installed software, or anything available via WMI queries.
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Local Group Policy
Local Group Policy (LGP, or LocalGPO) is a more basic version of Group Policy for standalone and non-domain computers, that has existed at least since Windows XP Home Edition, and can be applied to domain computers. Prior to Windows Vista, LGP could enforce a Group Policy Object for a single local computer, but could not make policies for individual users or groups. From Windows Vista onward, LGP allow Local Group Policy management for individual users and groups as well, and also allows backup, importing and exporting of policies between standalone machines via "GPO Packs" - group policy containers which include the files needed to import the policy to the destination machine.
Group Policy preferences
Group Policy Preferences are a way for the administrator to set policies that are not mandatory, but optional for the user or computer. There is a set of group policy setting extensions that were previously known as PolicyMaker. Microsoft bought PolicyMaker and then integrated them with Windows Server 2008. Microsoft has since released a migration tool that allows users to migrate PolicyMaker items to Group Policy Preferences.
Group Policy Preferences adds a number of new configuration items. These items also have a number of additional targeting options that can be used to granularly control the application of these setting items.
Group Policy Preferences are compatible with x86 and x64 versions of Windows XP, Windows Server 2003, and Windows Vista with the addition of the Client Side Extensions (also known as CSE).
Client Side Extensions are now included in Windows Server 2008, Windows 7, and Windows Server 2008 R2.
Group Policy Management Console
Originally, Group Policies were modified using the Group Policy Edit tool that was integrated with Active Directory Users and Computers Microsoft Management Console (MMC) snap-in, but it was later split into a separate MMC snap-in called the Group Policy Management Console (GPMC). The GPMC is now a user component in Windows Server 2008 and Windows Server 2008 R2 and is provided as a download as part of the Remote Server Administration Tools for Windows Vista and Windows 7.
Advanced Group Policy Management
Microsoft has also released a tool to make changes to Group Policy called Advanced Group Policy Management (a.k.a. AGPM). This tool is available for any organization that has licensed the Microsoft Desktop Optimization Pack (a.k.a. MDOP). This advanced tool allows administrators to have a check in/out process for modification Group Policy Objects, track changes to Group Policy Objects, and implement approval workflows for changes to Group Policy Objects.
AGPM consists of two parts - server and client. The server is a Windows Service that stores its Group Policy Objects in an archive located on the same computer or a network share. The client is a snap-in to the Group Policy Management Console, and connects to the AGPM server. Configuration of the client is performed via Group Policy.
Security
Group Policy settings are enforced voluntarily by the targeted applications. In many cases, this merely consists of disabling the user interface for a particular functions of accessing it.
Alternatively, a malevolent user can modify or interfere with the application so that it cannot successfully read its Group Policy settings, thus enforcing potentially lower security defaults or even returning arbitrary values.
Windows 8 enhancements
Windows 8 has introduced a new feature called Group Policy Update. This feature allows an administrator to force a group policy update on all computers with accounts in a particular Organizational Unit. This creates a scheduled task on the computer which runs the GPUPDATE command within 10 minutes, adjusted by a random offset to avoid overloading the domain controller.
Group Policy Infrastructure Status was introduced, which can report when any Group Policy Objects are not replicated correctly amongst domain controllers.
Group Policy Results Report also has a new feature that times the execution of individual components when doing a Group Policy Update.
Source of the article : Wikipedia
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