Performing a NIST 800-53 Security Assessment

NIST SP 800-53 provides a structured catalog of security and privacy controls for federal information systems. A security assessment evaluates how well these controls are implemented. Follow these steps to conduct an effective assessment:

1. Understand the Framework

Familiarize Yourself with NIST SP 800-53: Understand the structure, families, and types of controls (e.g., preventive, detective, corrective).
Identify the System Impact Level: Categorize the system using FIPS 199 and NIST SP 800-60 guidelines (Low, Moderate, or High impact).

2. Define Scope

Determine the System Boundary: Identify systems, subsystems, applications, and data to include in the assessment.
Identify Stakeholders: Engage system owners, security officers, and other relevant personnel.
Select Controls: Choose controls based on system categorization and risk.

3. Prepare for the Assessment

Develop an Assessment Plan: Document the purpose, scope, methods, and resources required.
Gather Documentation: Collect system security plans (SSPs), policies, previous audit reports, and procedures.

4. Perform the Assessment

Control Implementation Review:
- Verify that controls are implemented as described in the SSP.
- Use methods like interviews, documentation reviews, and operational observations.
Technical Testing:
- Conduct vulnerability scans and penetration tests to identify technical weaknesses.
Effectiveness Evaluation:
- Assess the controls’ ability to mitigate risks using test cases or predefined scenarios.

5. Document Findings

Identify Gaps and Weaknesses: Note controls that are partially implemented, not implemented, or ineffective.
Assess Risks: Evaluate risks associated with weaknesses in the system context.
Prioritize Remediation: Rank issues based on potential impact and likelihood of exploitation.

6. Develop a Security Assessment Report (SAR)

Include Key Components:
- Executive summary
- Assessment objectives and scope
- Findings and observations
- Risk assessment
- Recommendations for remediation
Provide Supporting Evidence: Attach test results, screenshots, and logs to substantiate findings.

7. Remediate and Mitigate Risks

Create a Plan of Action and Milestones (POA&M):
- Document remediation steps, responsible parties, and deadlines.
Implement Fixes: Address vulnerabilities and improve control implementations.
Monitor Progress: Ensure remediation efforts are on track.

8. Continuous Monitoring

Track Control Effectiveness: Use automated tools to monitor system security continuously.
Conduct Regular Assessments: Reevaluate controls periodically or after significant system changes.

Tools and Resources

Automated Tools: Use SCAP-compliant tools like Nessus or Qualys for technical control assessments.
Guidance: Refer to NIST SP 800-53A for detailed assessment procedures tailored to specific controls.

By following these steps, you can systematically evaluate your system’s security posture against the NIST SP 800-53 controls.