The mission of the DHS Chief Information Security Officer Directorate (DHS CISOD) is to support the Department's implementation of all applicable regulatory requirements—including the Federal Information Security Modernization Act (FISMA), relevant OMB circulars, Executive Orders, Federal laws, directives, policies, and regulations—while providing the Department of Homeland Security (DHS) a secure and trusted computing environment. Information security is an essential business function, critical to enabling DHS to conduct its operations and deliver service to the public. Leidos has a critical need for a Senior National Security Systems (NSS) Assessor to support the DHS Cyber Security Support Service Program. This role will execute security control assessments (SCAs) and provide risk analysis across highly sensitive NSS environments, ensuring compliance with CNSS, NIST, and DHS standards. The Senior NSS Assessor will deliver expert guidance to government stakeholders and contribute to the continuous improvement of cybersecurity posture for mission-critical systems.