NIST System and Communications Protection Risk Controls (sc)

Policy and Procedures (sc-1)

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

one or more,Organization-level,Mission/business process-level,System-level system and communications protection 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 system and communications protection policy and the associated system and communications protection controls;

Designate an organization-defined official to manage the development, documentation, and dissemination of the system and communications protection policy and procedures; and

Review and update the current system and communications protection:

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

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

System and communications protection policy and procedures address the controls in the SC 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 system and communications protection 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 system and communications protection 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.

Separation of System and User Functionality (sc-2)

Separate user functionality, including user interface services, from system management functionality.

System management functionality includes functions that are necessary to administer databases, network components, workstations, or servers. These functions typically require privileged user access. The separation of user functions from system management functions is physical or logical. Organizations may separate system management functions from user functions by using different computers, instances of operating systems, central processing units, or network addresses; by employing virtualization techniques; or some combination of these or other methods. Separation of system management functions from user functions includes web administrative interfaces that employ separate authentication methods for users of any other system resources. Separation of system and user functions may include isolating administrative interfaces on different domains and with additional access controls. The separation of system and user functionality can be achieved by applying the systems security engineering design principles in #sa-8(#sa-8), including [SA-8(1)](#sa-8.1), [SA-8(3)](#sa-8.3), [SA-8(4)](#sa-8.4), [SA-8(10)](#sa-8.10), [SA-8(12)](#sa-8.12), [SA-8(13)](#sa-8.13), [SA-8(14)](#sa-8.14), and [SA-8(18)](#sa-8.18).

Security Function Isolation (sc-3)

Isolate security functions from nonsecurity functions.

Security functions are isolated from nonsecurity functions by means of an isolation boundary implemented within a system via partitions and domains. The isolation boundary controls access to and protects the integrity of the hardware, software, and firmware that perform system security functions. Systems implement code separation in many ways, such as through the provision of security kernels via processor rings or processor modes. For non-kernel code, security function isolation is often achieved through file system protections that protect the code on disk and address space protections that protect executing code. Systems can restrict access to security functions using access control mechanisms and by implementing least privilege capabilities. While the ideal is for all code within the defined security function isolation boundary to only contain security-relevant code, it is sometimes necessary to include nonsecurity functions as an exception. The isolation of security functions from nonsecurity functions can be achieved by applying the systems security engineering design principles in #sa-8(#sa-8), including [SA-8(1)](#sa-8.1), [SA-8(3)](#sa-8.3), [SA-8(4)](#sa-8.4), [SA-8(10)](#sa-8.10), [SA-8(12)](#sa-8.12), [SA-8(13)](#sa-8.13), [SA-8(14)](#sa-8.14), and [SA-8(18)](#sa-8.18).

Information in Shared System Resources (sc-4)

Prevent unauthorized and unintended information transfer via shared system resources.

Preventing unauthorized and unintended information transfer via shared system resources stops information produced by the actions of prior users or roles (or the actions of processes acting on behalf of prior users or roles) from being available to current users or roles (or current processes acting on behalf of current users or roles) that obtain access to shared system resources after those resources have been released back to the system. Information in shared system resources also applies to encrypted representations of information. In other contexts, control of information in shared system resources is referred to as object reuse and residual information protection. Information in shared system resources does not address information remanence, which refers to the residual representation of data that has been nominally deleted; covert channels (including storage and timing channels), where shared system resources are manipulated to violate information flow restrictions; or components within systems for which there are only single users or roles.

Denial-of-service Protection (sc-5)

Protect against,Limit the effects of the following types of denial-of-service events: organization-defined types of denial-of-service events; and

Employ the following controls to achieve the denial-of-service objective: organization-defined controls by type of denial-of-service event.

Denial-of-service events may occur due to a variety of internal and external causes, such as an attack by an adversary or a lack of planning to support organizational needs with respect to capacity and bandwidth. Such attacks can occur across a wide range of network protocols (e.g., IPv4, IPv6). A variety of technologies are available to limit or eliminate the origination and effects of denial-of-service events. For example, boundary protection devices can filter certain types of packets to protect system components on internal networks from being directly affected by or the source of denial-of-service attacks. Employing increased network capacity and bandwidth combined with service redundancy also reduces the susceptibility to denial-of-service events.

Boundary Protection (sc-7)

Monitor and control communications at the external managed interfaces to the system and at key internal managed interfaces within the system;

Implement subnetworks for publicly accessible system components that are physically,logically separated from internal organizational networks; and

Connect to external networks or systems only through managed interfaces consisting of boundary protection devices arranged in accordance with an organizational security and privacy architecture.

Managed interfaces include gateways, routers, firewalls, guards, network-based malicious code analysis, virtualization systems, or encrypted tunnels implemented within a security architecture. Subnetworks that are physically or logically separated from internal networks are referred to as demilitarized zones or DMZs. Restricting or prohibiting interfaces within organizational systems includes restricting external web traffic to designated web servers within managed interfaces, prohibiting external traffic that appears to be spoofing internal addresses, and prohibiting internal traffic that appears to be spoofing external addresses. [SP 800-189](#f5edfe51-d1f2-422e-9b27-5d0e90b49c72) provides additional information on source address validation techniques to prevent ingress and egress of traffic with spoofed addresses. Commercial telecommunications services are provided by network components and consolidated management systems shared by customers. These services may also include third party-provided access lines and other service elements. Such services may represent sources of increased risk despite contract security provisions. Boundary protection may be implemented as a common control for all or part of an organizational network such that the boundary to be protected is greater than a system-specific boundary (i.e., an authorization boundary).

Access Points (sc-7.3)

External Telecommunications Services (sc-7.4)

Deny by Default ? Allow by Exception (sc-7.5)

Split Tunneling for Remote Devices (sc-7.7)

Route Traffic to Authenticated Proxy Servers (sc-7.8)

Fail Secure (sc-7.18)

Isolation of System Components (sc-7.21)

Transmission Confidentiality and Integrity (sc-8)

Protect the one or more,confidentiality,integrity of transmitted information.

Protecting the confidentiality and integrity of transmitted information applies to internal and external networks as well as any system components that can transmit information, including servers, notebook computers, desktop computers, mobile devices, printers, copiers, scanners, facsimile machines, and radios. Unprotected communication paths are exposed to the possibility of interception and modification. Protecting the confidentiality and integrity of information can be accomplished by physical or logical means. Physical protection can be achieved by using protected distribution systems. A protected distribution system is a wireline or fiber-optics telecommunications system that includes terminals and adequate electromagnetic, acoustical, electrical, and physical controls to permit its use for the unencrypted transmission of classified information. Logical protection can be achieved by employing encryption techniques. Organizations that rely on commercial providers who offer transmission services as commodity services rather than as fully dedicated services may find it difficult to obtain the necessary assurances regarding the implementation of needed controls for transmission confidentiality and integrity. In such situations, organizations determine what types of confidentiality or integrity services are available in standard, commercial telecommunications service packages. If it is not feasible to obtain the necessary controls and assurances of control effectiveness through appropriate contracting vehicles, organizations can implement appropriate compensating controls.

Cryptographic Protection (sc-8.1)

Network Disconnect (sc-10)

Terminate the network connection associated with a communications session at the end of the session or after organization-defined time period of inactivity.

Network disconnect applies to internal and external networks. Terminating network connections associated with specific communications sessions includes de-allocating TCP/IP address or port pairs at the operating system level and de-allocating the networking assignments at the application level if multiple application sessions are using a single operating system-level network connection. Periods of inactivity may be established by organizations and include time periods by type of network access or for specific network accesses.

Cryptographic Key Establishment and Management (sc-12)

Establish and manage cryptographic keys when cryptography is employed within the system in accordance with the following key management requirements: organization-defined requirements for key generation, distribution, storage, access, and destruction.

Cryptographic key management and establishment can be performed using manual procedures or automated mechanisms with supporting manual procedures. Organizations define key management requirements in accordance with applicable laws, executive orders, directives, regulations, policies, standards, and guidelines and specify appropriate options, parameters, and levels. Organizations manage trust stores to ensure that only approved trust anchors are part of such trust stores. This includes certificates with visibility external to organizational systems and certificates related to the internal operations of systems. [NIST CMVP](#1acdc775-aafb-4d11-9341-dc6a822e9d38) and [NIST CAVP](#84dc1b0c-acb7-4269-84c4-00dbabacd78c) provide additional information on validated cryptographic modules and algorithms that can be used in cryptographic key management and establishment.

Availability (sc-12.1)

Cryptographic Protection (sc-13)

Determine the organization-defined cryptographic uses; and

Implement the following types of cryptography required for each specified cryptographic use: organization-defined types of cryptography for each specified cryptographic use.

Cryptography can be employed to support a variety of security solutions, including the protection of classified information and controlled unclassified information, the provision and implementation of digital signatures, and the enforcement of information separation when authorized individuals have the necessary clearances but lack the necessary formal access approvals. Cryptography can also be used to support random number and hash generation. Generally applicable cryptographic standards include FIPS-validated cryptography and NSA-approved cryptography. For example, organizations that need to protect classified information may specify the use of NSA-approved cryptography. Organizations that need to provision and implement digital signatures may specify the use of FIPS-validated cryptography. Cryptography is implemented in accordance with applicable laws, executive orders, directives, regulations, policies, standards, and guidelines.

Collaborative Computing Devices and Applications (sc-15)

Prohibit remote activation of collaborative computing devices and applications with the following exceptions: organization-defined exceptions where remote activation is to be allowed; and

Provide an explicit indication of use to users physically present at the devices.

Collaborative computing devices and applications include remote meeting devices and applications, networked white boards, cameras, and microphones. The explicit indication of use includes signals to users when collaborative computing devices and applications are activated.

Public Key Infrastructure Certificates (sc-17)

Issue public key certificates under an organization-defined certificate policy or obtain public key certificates from an approved service provider; and

Include only approved trust anchors in trust stores or certificate stores managed by the organization.

Public key infrastructure (PKI) certificates are certificates with visibility external to organizational systems and certificates related to the internal operations of systems, such as application-specific time services. In cryptographic systems with a hierarchical structure, a trust anchor is an authoritative source (i.e., a certificate authority) for which trust is assumed and not derived. A root certificate for a PKI system is an example of a trust anchor. A trust store or certificate store maintains a list of trusted root certificates.

Mobile Code (sc-18)

Define acceptable and unacceptable mobile code and mobile code technologies; and

Authorize, monitor, and control the use of mobile code within the system.

Mobile code includes any program, application, or content that can be transmitted across a network (e.g., embedded in an email, document, or website) and executed on a remote system. Decisions regarding the use of mobile code within organizational systems are based on the potential for the code to cause damage to the systems if used maliciously. Mobile code technologies include Java applets, JavaScript, HTML5, WebGL, and VBScript. Usage restrictions and implementation guidelines apply to both the selection and use of mobile code installed on servers and mobile code downloaded and executed on individual workstations and devices, including notebook computers and smart phones. Mobile code policy and procedures address specific actions taken to prevent the development, acquisition, and introduction of unacceptable mobile code within organizational systems, including requiring mobile code to be digitally signed by a trusted source.

Secure Name/address Resolution Service (authoritative Source) (sc-20)

Provide additional data origin authentication and integrity verification artifacts along with the authoritative name resolution data the system returns in response to external name/address resolution queries; and

Provide the means to indicate the security status of child zones and (if the child supports secure resolution services) to enable verification of a chain of trust among parent and child domains, when operating as part of a distributed, hierarchical namespace.

Providing authoritative source information enables external clients, including remote Internet clients, to obtain origin authentication and integrity verification assurances for the host/service name to network address resolution information obtained through the service. Systems that provide name and address resolution services include domain name system (DNS) servers. Additional artifacts include DNS Security Extensions (DNSSEC) digital signatures and cryptographic keys. Authoritative data includes DNS resource records. The means for indicating the security status of child zones include the use of delegation signer resource records in the DNS. Systems that use technologies other than the DNS to map between host and service names and network addresses provide other means to assure the authenticity and integrity of response data.

Secure Name/address Resolution Service (recursive or Caching Resolver) (sc-21)

Request and perform data origin authentication and data integrity verification on the name/address resolution responses the system receives from authoritative sources.

Each client of name resolution services either performs this validation on its own or has authenticated channels to trusted validation providers. Systems that provide name and address resolution services for local clients include recursive resolving or caching domain name system (DNS) servers. DNS client resolvers either perform validation of DNSSEC signatures, or clients use authenticated channels to recursive resolvers that perform such validations. Systems that use technologies other than the DNS to map between host and service names and network addresses provide some other means to enable clients to verify the authenticity and integrity of response data.

Architecture and Provisioning for Name/address Resolution Service (sc-22)

Ensure the systems that collectively provide name/address resolution service for an organization are fault-tolerant and implement internal and external role separation.

Systems that provide name and address resolution services include domain name system (DNS) servers. To eliminate single points of failure in systems and enhance redundancy, organizations employ at least two authoritative domain name system servers?one configured as the primary server and the other configured as the secondary server. Additionally, organizations typically deploy the servers in two geographically separated network subnetworks (i.e., not located in the same physical facility). For role separation, DNS servers with internal roles only process name and address resolution requests from within organizations (i.e., from internal clients). DNS servers with external roles only process name and address resolution information requests from clients external to organizations (i.e., on external networks, including the Internet). Organizations specify clients that can access authoritative DNS servers in certain roles (e.g., by address ranges and explicit lists).

Session Authenticity (sc-23)

Protect the authenticity of communications sessions.

Protecting session authenticity addresses communications protection at the session level, not at the packet level. Such protection establishes grounds for confidence at both ends of communications sessions in the ongoing identities of other parties and the validity of transmitted information. Authenticity protection includes protecting against "man-in-the-middle" attacks, session hijacking, and the insertion of false information into sessions.

Fail in Known State (sc-24)

Fail to a organization-defined known system state for the following failures on the indicated components while preserving organization-defined system state information in failure: list of organization-defined types of system failures on organization-defined system components.

Failure in a known state addresses security concerns in accordance with the mission and business needs of organizations. Failure in a known state prevents the loss of confidentiality, integrity, or availability of information in the event of failures of organizational systems or system components. Failure in a known safe state helps to prevent systems from failing to a state that may cause injury to individuals or destruction to property. Preserving system state information facilitates system restart and return to the operational mode with less disruption of mission and business processes.

Protection of Information at Rest (sc-28)

Protect the one or more,confidentiality,integrity of the following information at rest: organization-defined information at rest.

Information at rest refers to the state of information when it is not in process or in transit and is located on system components. Such components include internal or external hard disk drives, storage area network devices, or databases. However, the focus of protecting information at rest is not on the type of storage device or frequency of access but rather on the state of the information. Information at rest addresses the confidentiality and integrity of information and covers user information and system information. System-related information that requires protection includes configurations or rule sets for firewalls, intrusion detection and prevention systems, filtering routers, and authentication information. Organizations may employ different mechanisms to achieve confidentiality and integrity protections, including the use of cryptographic mechanisms and file share scanning. Integrity protection can be achieved, for example, by implementing write-once-read-many (WORM) technologies. When adequate protection of information at rest cannot otherwise be achieved, organizations may employ other controls, including frequent scanning to identify malicious code at rest and secure offline storage in lieu of online storage.

Cryptographic Protection (sc-28.1)

Process Isolation (sc-39)

Maintain a separate execution domain for each executing system process.

Systems can maintain separate execution domains for each executing process by assigning each process a separate address space. Each system process has a distinct address space so that communication between processes is performed in a manner controlled through the security functions, and one process cannot modify the executing code of another process. Maintaining separate execution domains for executing processes can be achieved, for example, by implementing separate address spaces. Process isolation technologies, including sandboxing or virtualization, logically separate software and firmware from other software, firmware, and data. Process isolation helps limit the access of potentially untrusted software to other system resources. The capability to maintain separate execution domains is available in commercial operating systems that employ multi-state processor technologies.

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