Junior Security Engineer

Leidos LLC; Plyers Mill Estates (MD); On-site; USD 70,000 - 126,000; Full time

Job summary

Leidos seeks a Junior Security Engineer to support day-to-day security activities across enterprise and isolated environments. This on-site role involves vulnerability management, security monitoring, RMF/ATO activities and continuous security improvements.

You will collaborate with senior security personnel, system admins and engineers, gaining hands-on experience across DISA STIGs, SIEMs like Splunk and security tooling to maintain a strong security posture.

Qualifications

• Experience handling security requirements across front, middle, and back end components.
• Experience with Windows Server 2016/2019, Active Directory, IIS, DNS, DHCP, Exchange.
• Experience implementing security controls on common network services across distributed sites.
• Experience with networking tech and security assessment incl. STIGs.
• Experience with malware monitoring and tools like Splunk, ACAS; strong TCP/IP and encryption knowledge.

Responsibilities

• Perform day-to-day security activities under supervision and resolve blockers.
• Support vulnerability management from identification through closure with documentation.
• Perform vulnerability scanning and analysis using ACAS/Nessus or equivalent.
• Collaborate with Windows/Linux/Network teams for remediation and hardening.
• Implement and validate DISA STIGs and security baselines across infrastructure.
• Conduct security reviews, log reviews, and continuous monitoring activities.
• Assist RMF/ATO activities with security documentation and BoEs.
• Review changes for potential security impact and document findings.

Skills

Vulnerability management

Security monitoring

Windows/Linux

RMF/ATO

SIEM (Splunk)

Security+ or equivalent

Education

Bachelor's degree

Tools

ACAS

Tenable/Nessus

Splunk

McAfee HBSS

AD/ IIS / DNS basics

Job description

General program information and/or position overview. Leidos is seeking a Junior Security Engineer to support day‑to‑day security activities across enterprise and isolated environments. This position will provide hands‑on support for security operations, vulnerability management, RMF/ATO activities and continuous monitoring. The individual will work closely with senior security personnel, system administrators, engineers and other technical teams to implement security requirements, identify and remediate security issues and maintain the overall security posture of the environment. This position provides an opportunity to develop across multiple areas of cybersecurity, including vulnerability management, security engineering, RMF/ATO, system hardening and continuous monitoring. The individual will be given opportunities to take on increased technical responsibility as their knowledge and experience grow. This is a 100% on‑site position. All work must be performed at the customer site.

Primary Responsibilities

• Perform day‑to‑day security activities under the direction of senior security personnel and escape risks, technical issues and blockers as appropriate.
• Support vulnerability management activities from identification through closure, including analysis, remediation, validation and documentation.
• Perform vulnerability scanning and analyze findings using ACAS, Tenable/Nessus or equivalent technologies.
• Work with Windows, Linux, network, desktop support and other engineering teams to assist with vulnerability remediation and security‑related technical issues.
• Implement and validate DISA STIGs and approved security configuration baselines across infrastructure systems.
• Perform recurring security activities, including audit log reviews, account reviews, vulnerability reviews, security control validation and continuous monitoring.
• Support 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.
• Assist with reviewing system and configuration changes for potential security impact and document findings for review by senior security personnel and the ISSM.
• Support security activities 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 escalated identified issues as appropriate.
• Assist with maintaining security procedures, documentation, compliance evidence and vulnerability remediation records.
• Track assigned security findings, remediation activities and action items through completion and provide status updates as required.
• Participate in security reviews, engineering meetings and Technical Exchange Meetings (TEMs) as required.
• Research security vulnerabilities, technical requirements and remediation approaches and provide findings and recommendations to senior security personnel.
• Develop technical knowledge across the environment and take on increased responsibility for security activities as experience and proficiency grow.

Basic Qualifications

• 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).
• Bachelor's degree with at least 2 years of relevant experience.
• Additional years of experience may be considered in lieu of degree.
• 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

• CISSP or CASP Certification #NMECDTP‑Leidos

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.

Pay Range

• Pay Range $69,550.00 - $125,725.00

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.

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.

Pay and Benefits

Pay and benefits are fundamental to any career decision. That's why we craft compensation packages that reflect the importance of the work we do for our customers.

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

More details are available here.

Securing Your Data Leidos will never ask you to provide payment‑related information at any part of the employment application process. And Leidos will communicate with you only through emails that are sent from a Leidos.com email address. If you receive an email purporting to be from Leidos that asks for payment‑related information or any other personal information, please report the email to [e-mail].

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.

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.