We are seeking an experienced Information System Security Engineer (ISSO) / IT Systems Engineer to serve as the Classified Information Security Lead for the organization. This Arlingtonbased role is responsible for managing and safeguarding Secret and TopSecret information across diverse research and operational environments. Candidates must be U.S. citizens with an active Top Secret (TS) clearance and SCI eligibility. Role Responsibilities Serve as the primary lead for classified information security, ensuring full compliance with federal regulations governing the handling, storage, transmission, and protection of national security information. Maintain the security posture of classified and unclassified systems, including configuration, monitoring, and continuous improvement. Oversee cybersecurity compliance, documentation, and accreditation artifacts (e.g., security plans, risk assessments, POA&Ms). Execute contractspecific security duties supporting legal proceedings, research oper...