NIST SP 800-53 Rev. 5 Common Control Library

NIST control statement

a. Establish and document usage restrictions, configuration/connection requirements, and implementation guidance for each type of remote access allowed; and b. Authorize each type of remote access to the system prior to allowing such connections.

Discussion

Remote access is access to organizational systems (or processes acting on behalf of users) that communicate through external networks such as the Internet. Types of remote access include dial-up, broadband, and wireless. Organizations use encrypted virtual private networks (VPNs) to enhance confidentiality and integrity for remote connections. The use of encrypted VPNs provides sufficient assurance to the organization that it can effectively treat such connections as internal networks if the cryptographic mechanisms used are implemented in accordance with applicable laws, executive orders, directives, regulations, policies, standards, and guidelines. Still, VPN connections traverse external networks, and the encrypted VPN does not enhance the availability of remote connections. VPNs with encrypted tunnels can also affect the ability to adequately monitor network communications traffic for malicious code. Remote access controls apply to systems other than public web servers or systems designed for public access. Authorization of each remote access type addresses authorization prior to allowing remote access without specifying the specific formats for such authorization. While organizations may use information exchange and system connection security agreements to manage remote access connections to other systems, such agreements are addressed as part of [CA-3](#ca-3) . Enforcing access restrictions for remote access is addressed via [AC-3](#ac-3).

NIST control statement

Employ automated mechanisms to monitor and control remote access methods.

Discussion

Monitoring and control of remote access methods allows organizations to detect attacks and help ensure compliance with remote access policies by auditing the connection activities of remote users on a variety of system components, including servers, notebook computers, workstations, smart phones, and tablets. Audit logging for remote access is enforced by [AU-2](#au-2) . Audit events are defined in [AU-2a](#au-2_smt.a).

NIST control statement

Implement cryptographic mechanisms to protect the confidentiality and integrity of remote access sessions.

Discussion

Virtual private networks can be used to protect the confidentiality and integrity of remote access sessions. Transport Layer Security (TLS) is an example of a cryptographic protocol that provides end-to-end communications security over networks and is used for Internet communications and online transactions.

NIST control statement

Route remote accesses through authorized and managed network access control points.

Discussion

Organizations consider the Trusted Internet Connections (TIC) initiative [DHS TIC](#4f42ee6e-86cc-403b-a51f-76c2b4f81b54) requirements for external network connections since limiting the number of access control points for remote access reduces attack surfaces.

NIST control statement

(a) Authorize the execution of privileged commands and access to security-relevant information via remote access only in a format that provides assessable evidence and for the following needs: [Assignment: organization-defined needs] ; and (b) Document the rationale for remote access in the security plan for the system.

Discussion

Remote access to systems represents a significant potential vulnerability that can be exploited by adversaries. As such, restricting the execution of privileged commands and access to security-relevant information via remote access reduces the exposure of the organization and the susceptibility to threats by adversaries to the remote access capability.

NIST control statement

Withdrawn in this source release; review the official source for disposition.

NIST control statement

Protect information about remote access mechanisms from unauthorized use and disclosure.

Discussion

Remote access to organizational information by non-organizational entities can increase the risk of unauthorized use and disclosure about remote access mechanisms. The organization considers including remote access requirements in the information exchange agreements with other organizations, as applicable. Remote access requirements can also be included in rules of behavior (see [PL-4](#pl-4) ) and access agreements (see [PS-6](#ps-6)).

NIST control statement

Withdrawn in this source release; review the official source for disposition.

NIST control statement

Withdrawn in this source release; review the official source for disposition.

NIST control statement

Provide the capability to disconnect or disable remote access to the system within [Assignment: time period].

Discussion

The speed of system disconnect or disablement varies based on the criticality of missions or business functions and the need to eliminate immediate or future remote access to systems.

NIST control statement

Implement [Assignment: mechanisms] to authenticate [Assignment: remote commands].

Discussion

Authenticating remote commands protects against unauthorized commands and the replay of authorized commands. The ability to authenticate remote commands is important for remote systems for which loss, malfunction, misdirection, or exploitation would have immediate or serious consequences, such as injury, death, property damage, loss of high value assets, failure of mission or business functions, or compromise of classified or controlled unclassified information. Authentication mechanisms for remote commands ensure that systems accept and execute commands in the order intended, execute only authorized commands, and reject unauthorized commands. Cryptographic mechanisms can be used, for example, to authenticate remote commands.

NIST control statement

a. Identify the types of events that the system is capable of logging in support of the audit function: [Assignment: event types]; b. 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; c. Specify the following event types for logging within the system: [Assignment: 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]; d. 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 e. Review and update the event types selected for logging [Assignment: frequency].

Discussion

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.

NIST control statement

Develop a system-level continuous monitoring strategy and implement continuous monitoring in accordance with the organization-level continuous monitoring strategy that includes: a. Establishing the following system-level metrics to be monitored: [Assignment: system-level metrics]; b. Establishing [Assignment: frequencies] for monitoring and [Assignment: frequencies] for assessment of control effectiveness; c. Ongoing control assessments in accordance with the continuous monitoring strategy; d. Ongoing monitoring of system and organization-defined metrics in accordance with the continuous monitoring strategy; e. Correlation and analysis of information generated by control assessments and monitoring; f. Response actions to address results of the analysis of control assessment and monitoring information; and g. Reporting the security and privacy status of the system to [Assignment: organization-defined personnel or roles] [Assignment: organization-defined frequency].

Discussion

Continuous monitoring at the system level facilitates ongoing awareness of the system security and privacy posture to support organizational risk management decisions. The terms "continuous" and "ongoing" imply that organizations assess and monitor their controls and risks at a frequency sufficient to support risk-based decisions. Different types of controls may require different monitoring frequencies. The results of continuous monitoring generate risk response actions by organizations. When monitoring the effectiveness of multiple controls that have been grouped into capabilities, a root-cause analysis may be needed to determine the specific control that has failed. Continuous monitoring programs allow organizations to maintain the authorizations of systems and common controls in highly dynamic environments of operation with changing mission and business needs, threats, vulnerabilities, and technologies. Having access to security and privacy information on a continuing basis through reports and dashboards gives organizational officials the ability to make effective and timely risk management decisions, including ongoing authorization decisions. Automation supports more frequent updates to hardware, software, and firmware inventories, authorization packages, and other system information. Effectiveness is further enhanced when continuous monitoring outputs are formatted to provide information that is specific, measurable, actionable, relevant, and timely. Continuous monitoring activities are scaled in accordance with the security categories of systems. Monitoring requirements, including the need for specific monitoring, may be referenced in other controls and control enhancements, such as [AC-2g](#ac-2_smt.g), [AC-2(7)](#ac-2.7), [AC-2(12)(a)](#ac-2.12_smt.a), [AC-2(7)(b)](#ac-2.7_smt.b), [AC-2(7)(c)](#ac-2.7_smt.c), [AC-17(1)](#ac-17.1), [AT-4a](#at-4_smt.a), [AU-13](#au-13), [AU-13(1)](#au-13.1), [AU-13(2)](#au-13.2), [CM-3f](#cm-3_smt.f), [CM-6d](#cm-6_smt.d), [CM-11c](#cm-11_smt.c), [IR-5](#ir-5), [MA-2b](#ma-2_smt.b), [MA-3a](#ma-3_smt.a), [MA-4a](#ma-4_smt.a), [PE-3d](#pe-3_smt.d), [PE-6](#pe-6), [PE-14b](#pe-14_smt.b), [PE-16](#pe-16), [PE-20](#pe-20), [PM-6](#pm-6), [PM-23](#pm-23), [PM-31](#pm-31), [PS-7e](#ps-7_smt.e), [SA-9c](#sa-9_smt.c), [SR-4](#sr-4), [SC-5(3)(b)](#sc-5.3_smt.b), [SC-7a](#sc-7_smt.a), [SC-7(24)(b)](#sc-7.24_smt.b), [SC-18b](#sc-18_smt.b), [SC-43b](#sc-43_smt.b) , and [SI-4](#si-4).

NIST control statement

Centrally manage [Assignment: controls and related processes].

Discussion

Central management refers to organization-wide management and implementation of selected controls and processes. This includes planning, implementing, assessing, authorizing, and monitoring the organization-defined, centrally managed controls and processes. As the central management of controls is generally associated with the concept of common (inherited) controls, such management promotes and facilitates standardization of control implementations and management and the judicious use of organizational resources. Centrally managed controls and processes may also meet independence requirements for assessments in support of initial and ongoing authorizations to operate and as part of organizational continuous monitoring. Automated tools (e.g., security information and event management tools or enterprise security monitoring and management tools) can improve the accuracy, consistency, and availability of information associated with centrally managed controls and processes. Automation can also provide data aggregation and data correlation capabilities; alerting mechanisms; and dashboards to support risk-based decision-making within the organization. As part of the control selection processes, organizations determine the controls that may be suitable for central management based on resources and capabilities. It is not always possible to centrally manage every aspect of a control. In such cases, the control can be treated as a hybrid control with the control managed and implemented centrally or at the system level. The controls and control enhancements that are candidates for full or partial central management include but are not limited to: [AC-2(1)](#ac-2.1), [AC-2(2)](#ac-2.2), [AC-2(3)](#ac-2.3), [AC-2(4)](#ac-2.4), [AC-4(all)](#ac-4), [AC-17(1)](#ac-17.1), [AC-17(2)](#ac-17.2), [AC-17(3)](#ac-17.3), [AC-17(9)](#ac-17.9), [AC-18(1)](#ac-18.1), [AC-18(3)](#ac-18.3), [AC-18(4)](#ac-18.4), [AC-18(5)](#ac-18.5), [AC-19(4)](#ac-19.4), [AC-22](#ac-22), [AC-23](#ac-23), [AT-2(1)](#at-2.1), [AT-2(2)](#at-2.2), [AT-3(1)](#at-3.1), [AT-3(2)](#at-3.2), [AT-3(3)](#at-3.3), [AT-4](#at-4), [AU-3](#au-3), [AU-6(1)](#au-6.1), [AU-6(3)](#au-6.3), [AU-6(5)](#au-6.5), [AU-6(6)](#au-6.6), [AU-6(9)](#au-6.9), [AU-7(1)](#au-7.1), [AU-7(2)](#au-7.2), [AU-11](#au-11), [AU-13](#au-13), [AU-16](#au-16), [CA-2(1)](#ca-2.1), [CA-2(2)](#ca-2.2), [CA-2(3)](#ca-2.3), [CA-3(1)](#ca-3.1), [CA-3(2)](#ca-3.2), [CA-3(3)](#ca-3.3), [CA-7(1)](#ca-7.1), [CA-9](#ca-9), [CM-2(2)](#cm-2.2), [CM-3(1)](#cm-3.1), [CM-3(4)](#cm-3.4), [CM-4](#cm-4), [CM-6](#cm-6), [CM-6(1)](#cm-6.1), [CM-7(2)](#cm-7.2), [CM-7(4)](#cm-7.4), [CM-7(5)](#cm-7.5), [CM-8(all)](#cm-8), [CM-9(1)](#cm-9.1), [CM-10](#cm-10), [CM-11](#cm-11), [CP-7(all)](#cp-7), [CP-8(all)](#cp-8), [SC-43](#sc-43), [SI-2](#si-2), [SI-3](#si-3), [SI-4(all)](#si-4), [SI-7](#si-7), [SI-8](#si-8).

NIST control statement

Develop an organization-wide continuous monitoring strategy and implement continuous monitoring programs that include: a. Establishing the following organization-wide metrics to be monitored: [Assignment: metrics]; b. Establishing [Assignment: monitoring frequencies] and [Assignment: assessment frequencies] for control effectiveness; c. Ongoing monitoring of organizationally-defined metrics in accordance with the continuous monitoring strategy; d. Correlation and analysis of information generated by control assessments and monitoring; e. Response actions to address results of the analysis of control assessment and monitoring information; and f. Reporting the security and privacy status of organizational systems to [Assignment: organization-defined personnel or roles] [Assignment: organization-defined frequency].

Discussion

Continuous monitoring at the organization level facilitates ongoing awareness of the security and privacy posture across the organization to support organizational risk management decisions. The terms "continuous" and "ongoing" imply that organizations assess and monitor their controls and risks at a frequency sufficient to support risk-based decisions. Different types of controls may require different monitoring frequencies. The results of continuous monitoring guide and inform risk response actions by organizations. Continuous monitoring programs allow organizations to maintain the authorizations of systems and common controls in highly dynamic environments of operation with changing mission and business needs, threats, vulnerabilities, and technologies. Having access to security- and privacy-related information on a continuing basis through reports and dashboards gives organizational officials the capability to make effective, timely, and informed risk management decisions, including ongoing authorization decisions. To further facilitate security and privacy risk management, organizations consider aligning organization-defined monitoring metrics with organizational risk tolerance as defined in the risk management strategy. Monitoring requirements, including the need for monitoring, may be referenced in other controls and control enhancements such as, [AC-2g](#ac-2_smt.g), [AC-2(7)](#ac-2.7), [AC-2(12)(a)](#ac-2.12_smt.a), [AC-2(7)(b)](#ac-2.7_smt.b), [AC-2(7)(c)](#ac-2.7_smt.c), [AC-17(1)](#ac-17.1), [AT-4a](#at-4_smt.a), [AU-13](#au-13), [AU-13(1)](#au-13.1), [AU-13(2)](#au-13.2), [CA-7](#ca-7), [CM-3f](#cm-3_smt.f), [CM-6d](#cm-6_smt.d), [CM-11c](#cm-11_smt.c), [IR-5](#ir-5), [MA-2b](#ma-2_smt.b), [MA-3a](#ma-3_smt.a), [MA-4a](#ma-4_smt.a), [PE-3d](#pe-3_smt.d), [PE-6](#pe-6), [PE-14b](#pe-14_smt.b), [PE-16](#pe-16), [PE-20](#pe-20), [PM-6](#pm-6), [PM-23](#pm-23), [PS-7e](#ps-7_smt.e), [SA-9c](#sa-9_smt.c), [SC-5(3)(b)](#sc-5.3_smt.b), [SC-7a](#sc-7_smt.a), [SC-7(24)(b)](#sc-7.24_smt.b), [SC-18b](#sc-18_smt.b), [SC-43b](#sc-43_smt.b), [SI-4](#si-4).

NIST control statement

a. Monitor the system to detect: 1. Attacks and indicators of potential attacks in accordance with the following monitoring objectives: [Assignment: monitoring objectives] ; and 2. Unauthorized local, network, and remote connections; b. Identify unauthorized use of the system through the following techniques and methods: [Assignment: techniques and methods]; c. Invoke internal monitoring capabilities or deploy monitoring devices: 1. Strategically within the system to collect organization-determined essential information; and 2. At ad hoc locations within the system to track specific types of transactions of interest to the organization; d. Analyze detected events and anomalies; e. Adjust the level of system monitoring activity when there is a change in risk to organizational operations and assets, individuals, other organizations, or the Nation; f. Obtain legal opinion regarding system monitoring activities; and g. Provide [Assignment: system monitoring information] to [Assignment: personnel or roles] [Selection (one-or-more): as needed; [Assignment: frequency] ].

Discussion

System monitoring includes external and internal monitoring. External monitoring includes the observation of events occurring at external interfaces to the system. Internal monitoring includes the observation of events occurring within the system. Organizations monitor systems by observing audit activities in real time or by observing other system aspects such as access patterns, characteristics of access, and other actions. The monitoring objectives guide and inform the determination of the events. System monitoring capabilities are achieved through a variety of tools and techniques, including intrusion detection and prevention systems, malicious code protection software, scanning tools, audit record monitoring software, and network monitoring software. Depending on the security architecture, the distribution and configuration of monitoring devices may impact throughput at key internal and external boundaries as well as at other locations across a network due to the introduction of network throughput latency. If throughput management is needed, such devices are strategically located and deployed as part of an established organization-wide security architecture. Strategic locations for monitoring devices include selected perimeter locations and near key servers and server farms that support critical applications. Monitoring devices are typically employed at the managed interfaces associated with controls [SC-7](#sc-7) and [AC-17](#ac-17) . The information collected is a function of the organizational monitoring objectives and the capability of systems to support such objectives. Specific types of transactions of interest include Hypertext Transfer Protocol (HTTP) traffic that bypasses HTTP proxies. System monitoring is an integral part of organizational continuous monitoring and incident response programs, and output from system monitoring serves as input to those programs. System monitoring requirements, including the need for specific types of system monitoring, may be referenced in other controls (e.g., [AC-2g](#ac-2_smt.g), [AC-2(7)](#ac-2.7), [AC-2(12)(a)](#ac-2.12_smt.a), [AC-17(1)](#ac-17.1), [AU-13](#au-13), [AU-13(1)](#au-13.1), [AU-13(2)](#au-13.2), [CM-3f](#cm-3_smt.f), [CM-6d](#cm-6_smt.d), [MA-3a](#ma-3_smt.a), [MA-4a](#ma-4_smt.a), [SC-5(3)(b)](#sc-5.3_smt.b), [SC-7a](#sc-7_smt.a), [SC-7(24)(b)](#sc-7.24_smt.b), [SC-18b](#sc-18_smt.b), [SC-43b](#sc-43_smt.b) ). Adjustments to levels of system monitoring are based on law enforcement information, intelligence information, or other sources of information. The legality of system monitoring activities is based on applicable laws, executive orders, directives, regulations, policies, standards, and guidelines.