NIST SP800-37.pdf

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• Enabling more consistent, comparable, and repeatable assessments of security controls in federal information systems;
• Promoting a better understanding of agency-related mission risks resulting from the operation of information systems; and
• Creating more complete, reliable, and trustworthy information for authorizing officials—to facilitate more informed security accreditation decisions.
Security certification and accreditation are important activities that support a risk management process and are an integral part of an agency’s information security program.
Security accreditation is the official management decision given by a senior agency official to authorize operation of an information system and to explicitly accept the risk to agency operations, agency assets, or individuals based on the implementation of an agreed-upon set of security controls. Required by OMB Circular A-130, Appendix III, security accreditation provides a form of quality control and challenges managers and technical staffs at all levels to implement the most effective security controls possible in an information system, given mission requirements, technical constraints, operational constraints, and cost/schedule constraints. By accrediting an information system, an agency official accepts responsibility for the security of the system and is fully accountable for any adverse impacts to the agency if a breach of security occurs. Thus, responsibility and accountability are core principles that characterize security accreditation.
It is essential that agency officials have the most complete, accurate, and trustworthy information possible on the security status of their information systems in order to make timely, credible, risk-based decisions on whether to authorize operation of those systems. The information and supporting evidence needed for security accreditation is developed during a detailed security review of an information system, typically referred to as security certification. Security certification is a comprehensive assessment of the management, operational, and technical security controls in an information system, made in support of security accreditation, to determine the extent to which the controls are implemented correctly, operating as intended, and producing the desired outcome with respect to meeting the security requirements for the system. The results of a security certification are used to reassess the risks and update the system security plan, thus providing the factual basis for an authorizing official to render a security accreditation decision.