Information Systems Security Engineer Leidos is seeking an experienced Information Systems Security Engineer (ISSE) to lead the security architecture, design, and deployment of mission-critical applications across unclassified, classified, and corporate networks. This role is highly dynamic, requiring a security SME who can bridge network boundaries across DTRA, DIA, and corporate infrastructures leveraging AWS multi-region and hybrid cloud environments. The ideal candidate will design robust Cross Domain Solutions (CDS) and ensure compliant application deployments across multiple government and commercial domains. Key Responsibilities - Cross Domain Architecture: Design, integrate, and test Cross Domain Solutions (CDS) allowing secure, policy-compliant data transfers and multi-level data sharing between unclassified and classified environments. - AWS Cloud Security: Engineer and maintain secure application architectures within AWS (Commercial, GovCloud, and Secret/Top Secret regions) using cloud-native security tools, IAM policies, and VPC configuration. - Multi-Agency Security Integration: Coordinate security compliance and boundary protection architectures across differing DTRA, DIA, and corporate infrastructures. - Secure Application Deployment: Oversee the secure deployment and integration of applications across both high-side and low-side systems, ensuring compatibility with both government networks and corporate enterprise baselines. - RMF & Compliance Management: Author and maintain System Security Plans (SSPs) and authorization artifacts within eMASS, aligning security controls across NIST 800-53, ICD 503, FedRAMP, and agency-specific overlays. - Vulnerability Management: Perform routine system audits, analyze vulnerability scans (e.g., ACAS/Nessus, AWS Security Hub, Prisma Cloud), and guide technical teams through STIG remediation and continuous monitoring. - Government Liaison: Serve as the primary security liaison with Authorizing Officials (AOs), ISSOs, and external stakeholders from DTRA, DIA, and corporate leadership to achieve and maintain reciprocity and Authority to Operate (ATO). Required Qualifications - U.S. Citizenship is required - Candidate must possess an active TS/SCI, or a Top Secret clearance with a current SSBI, and be eligible to obtain a TS/SCI w/ poly level clearance - Requires deep understanding of and ability to apply principles, theories, and concepts of technical domain and has broad understanding of other related specialty areas. - Typically requires BS degree and 4 - 8 years of prior relevant experience in order to operate within the scope contemplated by the level. Certifications, education and relevant work experience will be considered in lieu of a degree. - Cloud Expertise: Deep knowledge of AWS security controls,, Windows/Linux server administration, shared responsibility models, and cloud-native architecture across disparate security classification levels. - Agency-Specific Knowledge: Direct experience working within or interfacing with DTRA and DIA networks, security processes, and assessment/authorization lifecycles. Includes experience with VMware, Azure virtual desktop, and Citrix. - Experience with container platforms managed via Kubernetes and Docker. - CDS/Multi-Level Security: Deep understanding of Cross Domain Solution technologies, data labeling, guard configurations, and secure data transport mechanisms. - Hybrid Systems Engineering: Proven ability to securely integrate government mission systems with commercial/corporate infrastructures, maintaining strict data separation. Preferred Qualifications - Certifications: Active DoD 8570/8140 IAT/IASAE Level III certification (e.g., CISSP, CASP+). AWS Certified Security - Specialty or AWS Solutions Architect certification is highly preferred. Original Posting: July 8, 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. Pay Range: Pay Range $87,100.00 - $157,450.00 The Leidos pay range for this job level is a general guideline only and not a guarantee of compensation or salary. Additional factors considered in extending an offer include (but are not limited to) responsibilities of the job, education, experience, knowledge, skills, and abilities, as well as internal equity, alignment with market data, applicable bargaining agreement (if any), or other law.