Peraton Labs is seeking a poly cleared Senior Information System Security Officer for a mission-critical, highly complex HPC environment enabling research across multiple security domains. You will own day-to-day security operations aligned to RMF, drive continuous monitoring, maintain ATO posture, and partner closely with subcontractor and customer personnel. This position requires full-time on-site work in Laurel, or a customer site near College Park, MD. Key responsibilities may include Lead or co-lead ATO/reauthorization efforts for complex boundary systems Mentor junior ISSOs and shape security operations playbooks Perform risk analysis and author formal recommendations to leadership Drive security engineering outcomes by partnering with internal teams on scalable compliance patterns Brief senior internal and customer stakeholders on security posture, systemic risk trends, remediation burn-down, and authorization readiness Act as the Senior ISSO supporting the system security lifecycle across development, operations, and modernization Execute and maintain RMF activities (e.g., control implementation oversight, evidence collection, assessment support, POA&M management, continuous monitoring) Maintain security authorization artifacts (e.g., SSP, control narratives, diagrams, inheritance/leverage controls, CM plan, incident handling plan, contingency artifacts, user/admin procedures) Operate continuous monitoring: vulnerability management, config compliance, patching coordination, scan result triage, risk acceptance, and remediation verification. Review and approve security-relevant changes through configuration/change control and validate security configurations after major upgrades Support incident response and reporting: participate in investigations, coordinate containment actions, preserve evidence, and contribute to post-incident lessons learned Ensure least privilege/access governance: account management oversight, privileged access workflows, periodic access reviews, and audit compliance requirements Translate security requirements into implementation guidance that engineering teams can operationalize (clear, testable, and automatable where possible)