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Advanced Security Auditing FAQ

Updated: June 22, 2011

Applies To: Windows 7, Windows Server 2008, Windows Server 2008 R2, Windows Vista

This topic for the IT professional lists questions and their answers about understanding, deploying, and managing security audit policies.

Security auditing is a methodical examination and review of activities that may affect the security of a system. In Windows, security auditing is more narrowly defined as the features and services that enable an administrator to log and review events for specified security-related activities.

Hundreds of events occur as the Windows operating system and the applications that run on it perform their tasks. These events can provide valuable information to help administrators troubleshoot and investigate security-related activities.

The basic security audit policy settings in Security Settings\Local Policies\Audit Policy and the advanced security audit policy settings in Security Settings\Advanced Audit Policy Configuration\System Audit Policies appear to overlap, but they are recorded and applied differently. When you apply basic audit policy settings to the local computer using Local Security Policy, you are editing the effective audit policy, so changes made to basic audit policy settings will appear exactly as configured in Auditpol.exe.

There are a number of additional differences between the security audit policy settings in these two locations.

There are nine basic audit policy settings under Security Settings\Local Policies\Audit Policy and 53 settings under Advanced Audit Policy Configuration. The settings available in Security Settings\Advanced Audit Policy Configuration address similar issues as the basic nine settings in Local Policies\Audit Policy but allow administrators to be more selective in the number and types of events to audit. For example, where basic audit policy provides a single setting for account logon, advanced audit policy provides four. Enabling the single basic account logon setting would be the equivalent of setting all four advanced account logon settings. In comparison, setting a single advanced audit policy setting does not generate audit events for activities you are not interested in. In addition, if you enable success auditing for the basic Audit account logon events setting, only success events will be logged for all account logon–related behaviors. In comparison, you can configure success auditing for one advanced account logon setting, failure auditing for a second advanced account logon setting, Success and failure auditing for a third advanced account logon setting—or no auditing, depending on the needs of your organization.

The nine basic settings under Security Settings\Local Policies\Audit Policy were introduced in Windows 2000, and therefore are available to all versions of Windows released since then. The advanced audit policy settings were introduced in Windows Vista and Windows Server 2008. The advanced settings can only be used on computers running Windows 7, Windows Vista, Windows Server 2008 R2, or Windows Server 2008.

noteNote
In Windows Vista and Windows Server 2008, advanced audit event settings were not integrated with Group Policy and could only be deployed by using logon scripts generated with the Auditpol.exe command-line tool. In Windows Server 2008 R2 and Windows 7, all auditing capabilities are integrated with Group Policy. This allows administrators to configure, deploy, and manage these settings in the Group Policy Management Console (GPMC) or Local Security Policy snap-in for a domain, site, or organizational unit (OU).

Basic audit policy is not compatible with advanced audit policy settings that are applied by using Group Policy in Windows Server 2008 R2 and Windows 7. This is because as soon as advanced audit policy settings are applied by using Group Policy, the current computer's audit policy settings are cleared before the resulting advanced audit policy settings are applied. After you apply advanced audit policy settings by using Group Policy, you can only reliably set system audit policy for the computer by using the advanced audit policy settings.

Editing and applying the advanced audit policy settings in Local Security Policy modifies the local Group Policy Object (GPO), so changes made here may not be exactly reflected in Auditpol.exe if there are policies from other domain GPOs or logon scripts. Both types of policy can be edited and applied by using domain GPOs, and these settings will override any conflicting local audit policy settings. However, because basic audit policy is recorded in the effective audit policy, the audit policy must be explicitly removed when a change is desired, or it will remain in the effective audit policy, whereas policy changes applied using local or domain Group Policy settings are reflected as soon as the new policy is applied.

ImportantImportant
Whether you apply advanced audit policy by using Group Policy or by using logon scripts, do not use both the basic audit policy settings under Local Policies\Audit Policy and the advanced settings under Security Settings\Advanced Audit Policy Configuration. Using both advanced and basic audit policy settings can cause unexpected results. If you use Advanced Audit Policy Configuration settings or use logon scripts (for computers running Windows Vista or Windows Server 2008) to apply advanced audit policy, be sure to enable the Audit: Force audit policy subcategory settings (Windows Vista or later) to override audit policy category settings policy setting under Local Policies\Security Options. This will prevent conflicts between similar settings by forcing basic security auditing to be ignored.

By default, policy options set in GPOs and linked to higher levels of Active Directory sites, domains, and OUs are inherited by all OUs at lower levels. However, inherited policy can be overridden by a GPO that is linked at a lower level.

For example, you might use a domain GPO to assign an organization-wide group of audit settings but want a certain OU to get a defined group of additional settings. To accomplish this, you can link a second GPO to that specific lower-level OU. Therefore, a logon audit setting that is applied at the OU level will override a conflicting logon audit setting that is applied at the domain level (unless you have taken special steps to apply Group Policy loopback processing).

The rules that govern how Group Policy settings are applied propagate to the subcategory level of audit policy settings. This means that audit policy settings configured in different GPOs will be merged, as long as no policy settings configured at a lower level exist. The following table illustrates this behavior.

 

Auditing subcategory Setting configured in an OU GPO (higher priority) Setting configured in a domain GPO (lower priority) Resulting policy for the target computer

Detailed File Share Auditing

Success

Failure

Success

Process Creation Auditing

Disabled

Success

Disabled

Logon Auditing

Success

Failure

Failure

All objects in Active Directory Domain Services (AD DS), and all securable objects on a local computer or on the network, have security descriptors to help control access to the objects. Security descriptors include information about who owns an object, who can access it and in what way, and what types of access are audited. Security descriptors, in turn, contain the access control list (ACL) of an object, which includes all of the security permissions that apply to that object. An object's security descriptor can contain two types of ACLs:

  • A DACL that identifies the users and groups who are allowed or denied access.

  • A SACL that controls how access is audited.

The access control model that is used in Windows is administered at the object level by setting different levels of access, or permissions, to objects. If permissions are configured for an object, its security descriptor contains a DACL with security identifiers (SIDs) for the users and groups that are allowed or denied access.

If auditing is configured for the object, its security descriptor also contains a SACL that controls how the security subsystem audits attempts to access the object. However, auditing is not completely configured unless a SACL has been configured for an object and a corresponding Object Access audit policy setting has been configured and applied.

In Windows security auditing, the computer, objects on the computer, and related resources are the primary recipients of actions by clients including applications, other computers, and users. Malicious users can use alternate credentials to hide their identity, and malicious applications can impersonate legitimate users to perform undesired tasks. Therefore, the most consistent way to apply audit policy is to focus on the computer and the objects and resources on that computer.

In addition, because audit policy capabilities can vary between computers running different versions of Windows, the best way to ensure that the audit policy is applied correctly is to base these settings on the computer instead of the user.

However, in cases where you want audit settings to apply only to specified groups of users, you can accomplish this by configuring SACLs on the relevant objects to enable auditing for a security group that contains only the users you specify. For example, you can configure a SACL on a folder called Payroll Data to enable auditing on attempts by members of the Payroll Processors OU to delete objects from this folder on Accounting Server 1. The Object Access\Audit File System audit policy setting applies to all of Accounting Server 1, but because it requires a corresponding resource SACL, only actions by members of the Payroll Processors OU on the Payroll Data folder generates audit events.

Basic audit policy settings are available in all versions of Windows since Windows 2000 and can be applied locally or by using Group Policy. Advanced audit policy settings were introduced in Windows Vista and Windows Server 2008, but the settings can only be applied by using logon scripts. In Windows 7 and Windows Server 2008 R2, advanced audit policy settings can be configured and applied by using local and domain Group Policy settings.

To use advanced audit policy settings, your domain controller must be installed on a computer running Windows Server 2008 R2, Windows Server 2008, or Windows Server 2003 with Service Pack 2 (SP2). Windows 2000 Server is not supported.

A success audit event is triggered when a defined action, such as accessing a file share, is completed successfully.

A failure audit event is triggered when a defined action, such as a user logon, is not completed successfully.

The appearance of failure audit events in the event log does not necessarily mean that something is wrong with your system. For example, if you configure Audit Logon events, a failure event may simply mean that a user mistyped his or her password.

System administrators and auditors increasingly want to verify that auditing policy is applied to all objects on a system. This has been difficult to accomplish because the system access control lists (SACLs) that govern auditing are applied on a per-object basis. Thus, to verify that an audit policy has been applied to all objects, you would have to check every single object and that no changes have been made, even temporarily, to even a single SACL.

In Windows Server 2008 R2 and Windows 7, administrators can define computer-wide global object access auditing policy for either the entire file system or registry on a computer. The specified SACL is then automatically applied to every single object of that type. This can be useful both for verifying that all critical files, folders, and registry settings on a computer are protected, and for identifying when an issue with a system resource occurs. If both a file or folder SACL and a global object access auditing policy (or a single registry setting SACL and a global object access auditing policy) are configured on a computer, the effective SACL is derived from combining the file or folder SACL and the global object access auditing policy. This means that an audit event is generated if an activity matches either the file or folder SACL or the global object access auditing policy.

Oftentimes it is not enough to know simply that an object such as a file or folder was accessed. You may also want to know why the user was able to access this resource. In Windows Server 2008 R2 and Windows 7, you can obtain this forensic data by configuring the Audit Handle Manipulation setting along with either the Audit File System or Audit Registry audit settings. For more information, see "Step 3: Creating and verifying an audit policy that provides the reason for object access" in the Advanced Security Audit Policy Step-by-Step Guide.

To track access control changes on computers running Windows 7, Windows Server 2008 R2, Windows Vista, or Windows Server 2008, you need to enable the following settings to track changes to discretionary access control lists (DACLs):

  • The Audit File System subcategory enabled for success, failure, or success and failure.

  • The Audit Authorization Policy Change setting enabled for success, failure, or success and failure.

  • A SACL with Write and Take ownership permissions applied to the object you want to monitor.

In Windows XP and Windows Server 2003, you need to use the Audit policy change subcategory.

Applying advanced audit policy settings replaces any comparable basic security audit policy settings. If you subsequently change the advanced audit policy setting to Not configured, you will need to complete the following steps to restore the original basic security audit policy settings:

  1. Set all Advanced Audit Policy sub-categories to Not configured.

  2. Delete all audit.csv files from the %SYSVOL% folder on the domain controller.

  3. Reconfigure and apply the basic audit policy settings.

Unless you complete all of these steps, the basic audit policy settings will not be restored.

Changes to security audit policy are critical security events. You can use the Audit Audit Policy Change setting to determine whether the operating system generates audit events when the following types of activities take place:

  • Permissions and audit settings on the audit policy object are changed.

  • The system audit policy is changed.

  • Security event sources are registered or unregistered.

  • Per-user audit settings are changed.

  • The value of CrashOnAuditFail is modified.

  • Audit settings on a file or registry key are changed.

  • A Special Groups list is changed.

Finding the right balance between auditing enough network and computer activity and auditing too little network and computer activity can be challenging. You can achieve this balance by identifying the most important resources, critical activities, and users or groups of users and designing a security audit policy that targets these resources, activities, and users. Useful guidelines and recommendations for developing an effective security auditing strategy can be found in Planning and Deploying Advanced Security Audit Policies.

The integration of advanced audit policy settings with domain Group Policy in Windows 7 and Windows Server 2008 R2 is designed to simplify and management and implementation of security audit policy in an organization's network. As such, tools used to plan and deploy Group Policy for a domain can also be used to plan and deploy security audit policy.

On an individual computer, the Auditpol command-line tool can be used to complete a number of important audit policy–related management tasks. For more information, see Auditpol Help.

In addition, there are a number of computer management products, such as the Audit Collection Services in Microsoft System Center Operations Manager 2007, which can be used to collect and filter event data. For more information, see Audit Collection Services (ACS) (http://go.microsoft.com/fwlink/?LinkId=163436).

Users who examine the security event log for the first time can be a bit overwhelmed by the number of audit events that are stored there (which can quickly number in the thousands) and the structured information included for each audit event. Additional information about these events, and the settings used to generate them, can be obtained from the following resources:

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