Sr. ISSE TS/SCI Polygraph

Leidos has a new and exciting opportunity for a Sr. Inf ormation System Security Engineer in our Intel Sector's Cyber & Analytics Business Area (CABA) . Our talented team is at the forefront in Security Engineering, Computer Network Operations (CNO), Mission Software, Analytical Methods and Modeling, Signals Intelligence (SIGINT), and Cryptographic Key Management. At Leidos , we offer competitive benefits , including Paid Time Off, 11 paid Holidays, 401K with a 6% company match and immediate vesting, Flexible Schedules, Discounted Stock Purchase Plans, Technical Upskilling, Education and Training Support, Parental Paid Leave, and much more. Join us and make a difference in National Security!

*You must have an active TS/SCI Polygraph up front. Unfortunately, no exceptions.*

Leidos has an exciting opportunity for a Sr. Information System Security Engineer to join a high performing agile team using the Scaled Agile Framework (SAFe) methodology to support a fast-paced, complex program! Program execution follows DEVOPS best practices and employs robust development, test and production environments. Our team of security engineers support enhancements to system security architecture and cyber security capabilities; manage multiple system security plans for development, test and production systems following the Risk Management Framework (RMF); manage cross domain capabilities; and support Security Verification Testing (SVT) of relevant Type 1 devices. The contract provides system engineering, development, test, integration and operational support, and is focused on injecting new technology and adding advanced capabilities while continuing to support an on-going operational system.

You will provide support for adding new capabilities to a complex system with exacting interface, performance and security requirements. You will become part of a team of Security Engineers working on providing improvements to our operational, test, integration, and development systems and solving challenging issues on a large, significant program. The position requires a solid understanding of security practices and policies as well as hands‑on vulnerability testing experience.

You will have numerous responsibilities from day to day drawn from a wide array of activities. The strongest candidates will have experience working in these areas:

• Validating and verifying system security requirements and establishing system security designs for large-scale systems, major system elements, and interfacing systems that are part of a large complex network environment with geographically distributed components.
• Identifying and implementing appropriate information security architectures and functionality to ensure uniform application of security policy and enterprise solutions.
• Recommending and developing technical solutions, products, and standards based on current and desired system security architecture.
• Assessing and mitigating system security threats and risks throughout the program life cycle.
• Leading and/or contributing to the security planning, assessment, risk analysis, risk management, certification and awareness activities for various system and networking operations.
• Effectively collaborating with other internal technical experts on a day-to-day basis.
• Communicating with Program Managers and POCs from customer organizations when necessary, regarding Security issues of significant importance.
• Participating in Program Increment Planning and related agile team activities.
• Working closely with System Engineering, Test Engineering, and Integration teams to ensure that the hardware and software architecture and implementation meets security requirements.
• Analyzing and assessing system implementation against multiple security compliance policies and recommending and implementing enhancements.
• Evaluating security solutions to ensure they meet customer specified requirements for processing information.
• Evaluating the impact of new development on the operational security posture of the system.
• Evaluating, reviewing, and testing critical software.
• Proposing, assessing, coordinating, implementing, and enforcing information systems security policies, standards, and methodologies.
• Auditing and assessing system security configuration settings using common methodologies and tools.
• Managing and enforcing security strategies and policies that effect various components of geographically distributed systems.
• Providing configuration management for security-relevant information system software.
• Serving as a subject matter expert in security architecture to include providing advice to Program Managers, Customer technical experts, and internal program teams.
• Formulating security compliance requirements for new system features.
• Identifying and remediating security issues throughout the system.
• Supporting risk assessment, risk management, security control assessment, continuous monitoring, service design, and other IA program support functions.
• Working with development teams to enrich team-wide understanding of different types of vulnerabilities, attack vectors and remediation approaches.
• Planning and conducting security verification testing of relevant type 1 devices.

Basic Qualifications

• MS degree and 15 - 20 years of prior relevant experience.
• Must have a solid understanding of security practices and policies and hands-on vulnerability testing experience using Customer tools.
• Must have experience applying Risk Management Framework.
• Must have experience formulating and assessing IT security policy.
• Must have demonstrated knowledge of and experience with common security tools, such as Nessus, NMAP and Wireshark hardware/software security implementation, communication protocol, encryption techniques/tools, and web services.
• Must have experience with secure configurations of commonly used desktop and server operating systems.
• Must be comfortable working on multiple systems and components simultaneously in various configurations.
• Must have strong verbal and written communications skills.
• Must be committed to adopting and adhering to best practices.
• Must be able to effectively plan and prioritize tasking and communicate clearly regarding technical options and trade-offs.
• Must be capable of performing high quality work both independently and with a team in a fast-moving environment.

Preferred Qualifications

• Five (5) years of experience with Defense in Depth Principals/technology (including access control, authorization, identification and authentication, public key infrastructure, network and enterprise security architecture) and applying risk assessment methodology to system development.
• DoD 8570 compliance with IASAE Level 2 or 3.
• Information Systems Security Engineering Professional (ISSEP) Certification.
• Computer Information Systems Security Professional (CISSP) Certification.
• Experience developing/implementing integrated security services management processes, such as assessing and auditing network penetration testing, anti-virus planning assistance, risk analysis, and incident response.
• Experience providing information assurance support for application development that includes system security certifications and project evaluations for firewalls that encompass the development, design, and implementation.
• Experience with penetration testing tools.
• Experience with scripting languages.

If you're looking for comfort, keep scrolling. At Leidos, we outthink, outbuild, and outpace the status quo - because the mission demands it. We're not hiring followers. We're recruiting the ones who disrupt, provoke, and refuse to fail. Step 10 is ancient history. We're already at step 30 - and moving faster than anyone else dares.

Original Posting:

June 24, 2026

Pay Range:

Pay Range $154,050.00 - $278,475.00

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.

About Leidos

Leidos is an industry and technology leader serving government and commercial customers with smarter, more efficient digital and mission innovations. Headquartered in Reston, Virginia, with 47,000 global employees, Leidos reported annual revenues of approximately $16.7 billion for the fiscal year ended January 3, 2025. For more information, visit

Pay and Benefits

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All qualified applicants will receive consideration for employment without regard to sex, race, ethnicity, age, national origin, citizenship, religion, physical or mental disability, medical condition, genetic information, pregnancy, family structure, marital status, ancestry, domestic partner status, sexual orientation, gender identity or expression, veteran or military status, or any other basis prohibited by law. Leidos will also consider for employment qualified applicants with criminal histories consistent with relevant laws.