NIST Audit and Accountability Risk Controls (au)

Policy and Procedures (au-1)

Develop, document, and disseminate to organization-defined personnel or roles:

one or more,Organization-level,Mission/business process-level,System-level audit and accountability policy that:

Addresses purpose, scope, roles, responsibilities, management commitment, coordination among organizational entities, and compliance; and

Is consistent with applicable laws, executive orders, directives, regulations, policies, standards, and guidelines; and

Procedures to facilitate the implementation of the audit and accountability policy and the associated audit and accountability controls;

Designate an organization-defined official to manage the development, documentation, and dissemination of the audit and accountability policy and procedures; and

Review and update the current audit and accountability:

Policy organization-defined frequency and following organization-defined events; and

Procedures organization-defined frequency and following organization-defined events.

Audit and accountability policy and procedures address the controls in the AU family that are implemented within systems and organizations. The risk management strategy is an important factor in establishing such policies and procedures. Policies and procedures contribute to security and privacy assurance. Therefore, it is important that security and privacy programs collaborate on the development of audit and accountability policy and procedures. Security and privacy program policies and procedures at the organization level are preferable, in general, and may obviate the need for mission- or system-specific policies and procedures. The policy can be included as part of the general security and privacy policy or be represented by multiple policies that reflect the complex nature of organizations. Procedures can be established for security and privacy programs, for mission or business processes, and for systems, if needed. Procedures describe how the policies or controls are implemented and can be directed at the individual or role that is the object of the procedure. Procedures can be documented in system security and privacy plans or in one or more separate documents. Events that may precipitate an update to audit and accountability policy and procedures include assessment or audit findings, security incidents or breaches, or changes in applicable laws, executive orders, directives, regulations, policies, standards, and guidelines. Simply restating controls does not constitute an organizational policy or procedure.

Event Logging (au-2)

Identify the types of events that the system is capable of logging in support of the audit function: organization-defined event types that the system is capable of logging;

Coordinate the event logging function with other organizational entities requiring audit-related information to guide and inform the selection criteria for events to be logged;

Specify the following event types for logging within the system: organization-defined event types (subset of the event types defined in [AU-2a.](#au-2_smt.a)) along with the frequency of (or situation requiring) logging for each identified event type;

Provide a rationale for why the event types selected for logging are deemed to be adequate to support after-the-fact investigations of incidents; and

Review and update the event types selected for logging organization-defined frequency.

An event is an observable occurrence in a system. The types of events that require logging are those events that are significant and relevant to the security of systems and the privacy of individuals. Event logging also supports specific monitoring and auditing needs. Event types include password changes, failed logons or failed accesses related to systems, security or privacy attribute changes, administrative privilege usage, PIV credential usage, data action changes, query parameters, or external credential usage. In determining the set of event types that require logging, organizations consider the monitoring and auditing appropriate for each of the controls to be implemented. For completeness, event logging includes all protocols that are operational and supported by the system. To balance monitoring and auditing requirements with other system needs, event logging requires identifying the subset of event types that are logged at a given point in time. For example, organizations may determine that systems need the capability to log every file access successful and unsuccessful, but not activate that capability except for specific circumstances due to the potential burden on system performance. The types of events that organizations desire to be logged may change. Reviewing and updating the set of logged events is necessary to help ensure that the events remain relevant and continue to support the needs of the organization. Organizations consider how the types of logging events can reveal information about individuals that may give rise to privacy risk and how best to mitigate such risks. For example, there is the potential to reveal personally identifiable information in the audit trail, especially if the logging event is based on patterns or time of usage. Event logging requirements, including the need to log specific event types, may be referenced in other controls and control enhancements. These include [AC-2(4)](#ac-2.4), [AC-3(10)](#ac-3.10), [AC-6(9)](#ac-6.9), [AC-17(1)](#ac-17.1), [CM-3f](#cm-3_smt.f), [CM-5(1)](#cm-5.1), [IA-3(3)(b)](#ia-3.3_smt.b), [MA-4(1)](#ma-4.1), [MP-4(2)](#mp-4.2), #pe-3(#pe-3), #pm-21(#pm-21), #pt-7(#pt-7), #ra-8(#ra-8), [SC-7(9)](#sc-7.9), [SC-7(15)](#sc-7.15), [SI-3(8)](#si-3.8), [SI-4(22)](#si-4.22), [SI-7(8)](#si-7.8), and [SI-10(1)](#si-10.1). Organizations include event types that are required by applicable laws, executive orders, directives, policies, regulations, standards, and guidelines. Audit records can be generated at various levels, including at the packet level as information traverses the network. Selecting the appropriate level of event logging is an important part of a monitoring and auditing capability and can identify the root causes of problems. When defining event types, organizations consider the logging necessary to cover related event types, such as the steps in distributed, transaction-based processes and the actions that occur in service-oriented architectures.

Content of Audit Records (au-3)

Ensure that audit records contain information that establishes the following:

What type of event occurred;

When the event occurred;

Where the event occurred;

Source of the event;

Outcome of the event; and

Identity of any individuals, subjects, or objects/entities associated with the event.

Audit record content that may be necessary to support the auditing function includes event descriptions (item a), time stamps (item b), source and destination addresses (item c), user or process identifiers (items d and f), success or fail indications (item e), and filenames involved (items a, c, e, and f) . Event outcomes include indicators of event success or failure and event-specific results, such as the system security and privacy posture after the event occurred. Organizations consider how audit records can reveal information about individuals that may give rise to privacy risks and how best to mitigate such risks. For example, there is the potential to reveal personally identifiable information in the audit trail, especially if the trail records inputs or is based on patterns or time of usage.

Additional Audit Information (au-3.1)

Audit Log Storage Capacity (au-4)

Allocate audit log storage capacity to accommodate organization-defined audit log retention requirements.

Organizations consider the types of audit logging to be performed and the audit log processing requirements when allocating audit log storage capacity. Allocating sufficient audit log storage capacity reduces the likelihood of such capacity being exceeded and resulting in the potential loss or reduction of audit logging capability.

Response to Audit Logging Process Failures (au-5)

Alert organization-defined personnel or roles within organization-defined time period in the event of an audit logging process failure; and

Take the following additional actions: organization-defined additional actions.

Audit logging process failures include software and hardware errors, failures in audit log capturing mechanisms, and reaching or exceeding audit log storage capacity. Organization-defined actions include overwriting oldest audit records, shutting down the system, and stopping the generation of audit records. Organizations may choose to define additional actions for audit logging process failures based on the type of failure, the location of the failure, the severity of the failure, or a combination of such factors. When the audit logging process failure is related to storage, the response is carried out for the audit log storage repository (i.e., the distinct system component where the audit logs are stored), the system on which the audit logs reside, the total audit log storage capacity of the organization (i.e., all audit log storage repositories combined), or all three. Organizations may decide to take no additional actions after alerting designated roles or personnel.

Audit Record Review, Analysis, and Reporting (au-6)

Review and analyze system audit records organization-defined frequency for indications of organization-defined inappropriate or unusual activity and the potential impact of the inappropriate or unusual activity;

Report findings to organization-defined personnel or roles; and

Adjust the level of audit record review, analysis, and reporting within the system when there is a change in risk based on law enforcement information, intelligence information, or other credible sources of information.

Audit record review, analysis, and reporting covers information security- and privacy-related logging performed by organizations, including logging that results from the monitoring of account usage, remote access, wireless connectivity, mobile device connection, configuration settings, system component inventory, use of maintenance tools and non-local maintenance, physical access, temperature and humidity, equipment delivery and removal, communications at system interfaces, and use of mobile code or Voice over Internet Protocol (VoIP). Findings can be reported to organizational entities that include the incident response team, help desk, and security or privacy offices. If organizations are prohibited from reviewing and analyzing audit records or unable to conduct such activities, the review or analysis may be carried out by other organizations granted such authority. The frequency, scope, and/or depth of the audit record review, analysis, and reporting may be adjusted to meet organizational needs based on new information received.

Automated Process Integration (au-6.1)

Correlate Audit Record Repositories (au-6.3)

Audit Record Reduction and Report Generation (au-7)

Provide and implement an audit record reduction and report generation capability that:

Supports on-demand audit record review, analysis, and reporting requirements and after-the-fact investigations of incidents; and

Does not alter the original content or time ordering of audit records.

Audit record reduction is a process that manipulates collected audit log information and organizes it into a summary format that is more meaningful to analysts. Audit record reduction and report generation capabilities do not always emanate from the same system or from the same organizational entities that conduct audit logging activities. The audit record reduction capability includes modern data mining techniques with advanced data filters to identify anomalous behavior in audit records. The report generation capability provided by the system can generate customizable reports. Time ordering of audit records can be an issue if the granularity of the timestamp in the record is insufficient.

Automatic Processing (au-7.1)

Time Stamps (au-8)

Use internal system clocks to generate time stamps for audit records; and

Record time stamps for audit records that meet organization-defined granularity of time measurement and that use Coordinated Universal Time, have a fixed local time offset from Coordinated Universal Time, or that include the local time offset as part of the time stamp.

Time stamps generated by the system include date and time. Time is commonly expressed in Coordinated Universal Time (UTC), a modern continuation of Greenwich Mean Time (GMT), or local time with an offset from UTC. Granularity of time measurements refers to the degree of synchronization between system clocks and reference clocks (e.g., clocks synchronizing within hundreds of milliseconds or tens of milliseconds). Organizations may define different time granularities for different system components. Time service can be critical to other security capabilities such as access control and identification and authentication, depending on the nature of the mechanisms used to support those capabilities.

Protection of Audit Information (au-9)

Protect audit information and audit logging tools from unauthorized access, modification, and deletion; and

Alert organization-defined personnel or roles upon detection of unauthorized access, modification, or deletion of audit information.

Audit information includes all information needed to successfully audit system activity, such as audit records, audit log settings, audit reports, and personally identifiable information. Audit logging tools are those programs and devices used to conduct system audit and logging activities. Protection of audit information focuses on technical protection and limits the ability to access and execute audit logging tools to authorized individuals. Physical protection of audit information is addressed by both media protection controls and physical and environmental protection controls.

Access by Subset of Privileged Users (au-9.4)

Audit Record Retention (au-11)

Retain audit records for organization-defined time period consistent with records retention policy to provide support for after-the-fact investigations of incidents and to meet regulatory and organizational information retention requirements.

Organizations retain audit records until it is determined that the records are no longer needed for administrative, legal, audit, or other operational purposes. This includes the retention and availability of audit records relative to Freedom of Information Act (FOIA) requests, subpoenas, and law enforcement actions. Organizations develop standard categories of audit records relative to such types of actions and standard response processes for each type of action. The National Archives and Records Administration (NARA) General Records Schedules provide federal policy on records retention.

Audit Record Generation (au-12)

Provide audit record generation capability for the event types the system is capable of auditing as defined in [AU-2a](#au-2_smt.a) on organization-defined system components;

Allow organization-defined personnel or roles to select the event types that are to be logged by specific components of the system; and

Generate audit records for the event types defined in [AU-2c](#au-2_smt.c) that include the audit record content defined in #au-3(#au-3).

Audit records can be generated from many different system components. The event types specified in [AU-2d](#au-2_smt.d) are the event types for which audit logs are to be generated and are a subset of all event types for which the system can generate audit records.

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