Knowledge of system security engineering principles, including system security design, authentication and authorization, system integration, risk management, intrusion detection, incident handling, configuration control, change management, auditing, security testing, and information assurance principles. August 31, 2026 For U.S. Positions: While subject to change based on business needs, Leidos reasonably anticipates that this job requisition will remain open for at least 3 days with an anticipated close date of no earlier than 3 days after the original posting date as listed above.