What is a System Security Plan (SSP)?

While there are various templates available (NIST provides a helpful one), a typical SSP contains several core components. It’s a detailed document, often running from 80 to over 150 pages, because it needs to be thorough.

Key sections of an SSP generally include:

• System Identification: Basic information about the system, its name, and its purpose.

• System Environment and Boundaries: A description of the system's mission, the data it processes, and a clear definition of its boundaries. This includes network diagrams, hardware and software inventories, and descriptions of any connections to other systems.

• Security Control Implementation: This is the heart of the SSP. This section details how each required security control (e.g., from NIST SP 800-171 or NIST SP 800-53) is implemented. If a control is not in place, it must be documented here.

• Roles and Responsibilities: A clear outline of who is responsible for the security of the system, from the system owner to the administrators.

• Plan of Action & Milestones (POA&M): If any security controls are not fully implemented, the POA&M is a separate but related document that tracks the plan to correct these deficiencies. It outlines the weakness, the planned remediation, resources required, and a timeline for completion.

• References to Policies and Procedures: The SSP will often reference other key security documents, like an Incident Response Plan, Configuration Management Plan, or personnel screening procedures.

Bad threat actors love to find the gaps in a security plan. An incomplete or outdated SSP often signals an organization with exploitable vulnerabilities.