Senior Security Engineer

Leidos LLC; Plyers Mill Estates (MD); On-site; USD 108,000 - 195,000; Full time

Benefits offered by this job

Health and Wellness programs

Paid Leave

Retirement benefits

Job summary

Leidos is seeking a Senior Security Engineer to serve as the technical lead for day-to-day security activities, including vulnerability management, RMF/ATO support, and continuous monitoring. This on-site role requires mentoring security staff and coordinating across infrastructure and engineering teams to maintain a strong security posture.

The position demands hands-on security engineering, direct support to security operations, and collaboration with the ISSM, customer, and program leadership

Qualifications

• Bachelor's degree in Computer Science, IT, or related field, or equivalent work experience.
• 8+ years of relevant security engineering/leadership experience.
• DoD 8570.11 IAT Level II certification required.

Responsibilities

• Lead and coordinate day-to-day security operations and set priorities for the team.
• Provide technical leadership to security personnel, system admins, and engineers.
• Oversee vulnerability management from identification to closure and documentation.
• Coordinate remediation across Windows, Linux, networks, and desktop support teams.
• Oversee vulnerability scanning with ACAS/Nessus and validate findings.
• Support RMF/ATO activities with proper documentation and evidence.

Skills

Security leadership

Vulnerability management

RMF/ATO knowledge

Team mentoring

Education

Bachelor's degree in Computer Science/IT or related field

DoD 8570.11 IAT Level II certification

Tools

ACAS

Nessus/Tenable

Splunk

McAfee HBSS

Job description

General program information and/or position overview. Leidos is seeking a Senior Security Engineer to serve as the technical lead for day-to-day security activities supporting enterprise and isolated environments. This position will provide technical leadership and oversight for security operations, vulnerability management, RMF/ATO support and continuous monitoring activities. The individual will lead and mentor security personnel, establish priorities and coordinate security activities across infrastructure and engineering teams. This is a hands‑on technical lead position, and the individual will be expected to directly support security engineering and operational security activities as needed. The individual will work closely with the ISSM, customer, program leadership and technical teams to translate security requirements into actionable work and maintain the overall security posture of the environment. This is a 100% on‑site position. All work must be performed at the customer site.

Primary Responsibilities

• Lead and coordinate day‑to‑day security operations, establish priorities and assign and track activities across the security team.
• Provide technical leadership and guidance to security personnel, system administrators, engineers and other technical teams.
• Lead vulnerability management from identification through closure, including analysis, prioritization, remediation, validation and documentation.
• Coordinate vulnerability remediation across Windows, Linux, network, desktop support and other engineering teams and provide hands‑on support for complex or high‑priority issues as needed.
• Oversee and perform vulnerability scanning and analysis using ACAS, Tenable/Nessus or equivalent technologies.
• Oversee implementation and validation of DISA STIGs and approved security configuration baselines across infrastructure systems.
• Ensure recurring security activities are performed, including audit log and account reviews, vulnerability reviews, security control validation and continuous monitoring.
• Support and oversee RMF/ATO activities, including security documentation, control evidence, Body of Evidence (BoE), POA&Ms and compliance with NIST SP 800‑53, ICD 503 and applicable security directives.
• Work with the ISSM to translate security and compliance requirements into technical and operational activities and evaluate system or configuration changes for potential security impact.
• Provide security oversight and technical support for isolated or restricted environments, including vulnerability scanning, logging, patching, hardening and security monitoring.
• Review security logs and events using Splunk or equivalent SIEM/log‑management technologies and ensure identified issues are appropriately addressed.
• Develop and maintain repeatable security processes and procedures for vulnerability management, compliance monitoring, evidence collection and security operations.
• Track security risks, deficiencies, remediation activities and compliance status and communicate status, risks and recommendations to customer and program leadership.
• Participate in Technical Exchange Meetings (TEMs), security reviews, engineering meetings and customer discussions related to system security and accreditation.
• Manage, supervise and mentor security and technical staff as assigned.

Basic Qualifications

• Bachelor’s degree in Computer Science, Information Technology, or a related field, or equivalent work experience.
• Experience with application performance and latency problems related to security requirements from front, middle, and back end.
• Working experience with Windows Server 2016/2019, Active Directory, IIS, DNS, DHCP, Exchange, DFS.
• Experience implementing security controls on common network services such as file, email, and active directory across multiple geographically dispersed sites.
• Experience with networking technologies and security assessment to include, but not limited to, STIGs.
• Experience implementing and supporting enterprise system security and malware monitoring and prevention tools such as Splunk, McAfee HBSS, and ACAS Solid network and systems troubleshooting experience with TCP/IP, Internet security, and encryption (data at rest, data in transit).
• Ability to produce clear and concise documents and diagrams capturing networking and operational procedures and LAN/WAN topology using MS Visio, MS Project, MS Excel and MS Word.
• Candidate must, at a minimum, meet DoD 8570.11‑ IAT Level II certification requirements (currently Security+ CE, CCNA‑Security, GSEC, or SSCP along with an appropriate computing environment (CE) certification).

Education/Experience Requirements

• Candidate must have a Bachelor's, with at least 8 years of relevant experience. Additional years of experience may be considered in lieu of degree.

Clearance

Active TS/SCI clearance with Polygraph required OR active TS/SCI and willingness to get a Poly. US Citizenship is required due to the nature of the government contracts we support.

Preferred Qualifications

• Experience managing and/or supervising a team of technical professionals.
• CISSP or CASP Certification.
• #NMECDTP‑Leidos.

About Leidos

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 Information

Original Posting: September 14, 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 $107,900.00 - $195,050.00
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.

Pay Range

Pay Range $107,900.00 - $195,050.00

Benefits

Employment benefits include competitive compensation, Health and Wellness programs, Income Protection, Paid Leave and Retirement.

Commitment and Diversity

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.

Company Overview

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 $17.2 billion for the fiscal year ended January 2, 2026. For more information, visit www.Leidos.com.