Jobs in the United States

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Added 35 mins ago
Senior Director, Software and Quality Engineering
OneStream
United States
OneStream is the AI operating system for modern finance. As Sr. Director, Software and Quality Engineering, you will lead our unified software development and quality engineering…
Added 36 mins ago
Sr Tech Support Engineer MI -1 (for medical imaging devices)
Fujifilm
Jefferson City, MO
The Senior Technical Support Engineer, MI - I (Tier 1) provides highly visible remote technical support across our product lines for HCUS customers. This role focuses on more complex issue…
Added 59 mins ago
L
Combat Management Systems Engineer
Lyntris
San Diego, CA
- $120,000 to $160,000 USD / year
…expertise within their domain. Combining differentiated hardware, software and mission expertise, Lyntris helps customers sense threats, make sense of complex conditions and act with…
Added 1 hour ago
TT
Senior Security Engineer
True Talent Solutions Partners
San Francisco, CA
- $190,000 to $250,000 USD / year
Join a growing AI-focused fintech team as a hands-on Senior Security Engineer, owning and advancing application security in a regulated banking environment. This individual contributor role…
Added 1 hour ago
Software Engineer Principal
SAIC
Remote, United States
Candidates must have the ability to get a Secret Security clearance
Added 1 hour ago
System Engineer
SAIC
Stafford, VA
Systems safety analysis of hardware and software for US Marines Corps weapons systems.
Added 1 hour ago
Senior Systems Integration Engineer - Secret
Parsons Corporation
Centreville, VA
Must have an active Secret clearance · Must have a Valid US Passport
Added 1 hour ago
DevOps Engineer
Parsons Corporation
Centreville, VA
…collaborative team that analyzes, designs, and develops computer software to support marquee customers in Defense and Intelligence. We are seeking a DevOps Engineer (CNO) to develop and…
Added 1 hour ago
Software Test Engineer (Level 2 or 3) AHT
Northrop Grumman
Dulles, VA
Northrop Grumman Space Systems is seeking a Software Test Engineer to support the verification and validation of mission-critical satellite ground software. In this role, you will develop &…
Added 1 hour ago
Network Security Engineer
SAIC
Suffolk, VA
SAIC is seeking a Network Security Engineer with experience in US Navy IT networks to support the sustained operation and maintenance of a newly deployed naval enterprise transport network,…
Added 1 hour ago
Test Engineer (Journeyman)
CACI International
Ashburn, VA
CACI is seeking a Journeyman Test Engineer for the Global Mission Operations Support (GMOS) contract, supporting the Department of State. This role offers a unique opportunity to enhance…
Added 1 hour ago
Network Engineer III
CACI International
Springfield, VA
Team CACI has an exciting and challenging opportunity available for a Network Engineer who performs research, requirements analysis, design, installation, documentation, troubleshooting,…
Added 1 hour ago
A/AI Machine Learning Engineer
Lockheed Martin
Manassas, VA
Bachelor's or Master's Degree is Software Engineering, Computer Science, Machine Learning, or related STEM degree
Added 1 hour ago
Full Stack Software Developer/Engineer
CACI International
Sterling, VA
Clearance: Must have TS/SCI with CI poly (or be willing to take CI poly)
Added 1 hour ago
Principal Network Engineer / Senior Principal Network Engineer
Northrop Grumman
Chantilly, VA
At the heart of Defining Possible is our commitment to missions. In rapidly changing global security environments, Northrop Grumman brings informed insights and software-secure technology…
Added 1 hour ago
Expert Software Engineer
ManTech
Herndon, VA
MANTECH seeks a motivated, career and customer-oriented Expert Software Engineer to join our team in Herndon VA . This role supports the development and enhancement of mission-critical…
Added 1 hour ago
Mech Colo Regional Engineer , Colocation Region Engineering- AMER
Amazon
Herndon, VA
You’ll join a diverse team of software, hardware, and network engineers, supply chain specialists, security experts, operations managers, and other vital roles. You’ll collaborate with…
Added 1 hour ago
Mech Colo Regional Engineer , Colocation Region Engineering- AMER
Amazon
Herndon, VA
You’ll join a diverse team of software, hardware, and network engineers, supply chain specialists, security experts, operations managers, and other vital roles. You’ll collaborate with…
Added 1 hour ago
IG
Remote AI Engineer
Insight Global
Norfolk, VA
- $56 to $82 USD / hour
Insight Global is seeking a qualified Remote AI Engineer in support of one of our large federal clients in Norfolk, VA. This candidate will be responsible for designing, building, and…
Added 1 hour ago
Naval Architect Engineer 3 - 30097 1
Huntington Ingalls Industries
Virginia Beach, VA
…vehicles (UUVs), unmanned surface vehicles (USVs) and autonomy…
Added 1 hour ago
Advanced Training Systems Acquisition Engineer (Engineering Technician 3) - 31115
Huntington Ingalls Industries
Virginia Beach, VA
What You Must Have · Candidate must have experience in Navy combat systems modernization aligned with the Navy Modernization Process (NMP) framework
Added 1 hour ago
Senior Linux System Administrator
Altamira Technology Corporation
Chantilly, VA · McLean, VA
We focus on recruiting talented, self-motivated employees that strive to find a way to get things done. Join our team of experts as we engineer national security!
Added 1 hour ago
Senior Network Engineer
Altamira Technology Corporation
Chantilly, VA · McLean, VA
We are seeking a Senior Network Engineer responsible for configuration, implementation, maintenance, and troubleshooting of a critical operational network. Provides an engineering resource…
Added 1 hour ago
Linux Systems Engineer
SAIC
Arlington, VA
SAIC is seeking a Linux Systems Engineer capable of working with contractors, government personnel, and subject matter experts focusing on creating and recognizing targeting opportunities…
Added 1 hour ago
DSCA Data Engineer Mid (Software Development Analyst) - 31121
Huntington Ingalls Industries
Arlington, VA
Clearance: Must possess and maintain an active Secret clearance at the time of consideration

Castelion Corporation

Information System Security Engineer (ISSE)

Torrance, CA, United States
Torance, CA, United States

Apply on job-boards.greenhouse.io About employer

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Job details

Posting language: English
Posted: Nov 3, 2026

Original job description

Why Castelion, Why Now

Castelion is moving incredibly fast to develop and deliver advanced defense systems at a time when execution matters more than ever. We believe focus, ownership, and excellence are decisive advantages - and we're building a world-class team to turn bold ideas into real capability.

This is a rare opportunity to join at an early stage, where you'll have significant ownership, collaborate with exceptional teammates, and make a direct, measurable impact on our mission and the future of the company - regardless of your function.

Information System Security Engineer

The Information System Security Engineer (ISSE) at Castelion is responsible for translating security requirements into tested controls for classified information systems. In this role, you will harden systems and networks, configure security tools, investigate findings, and work with Information System Security Managers (ISSMs), Information System Security Officers (ISSOs), and IT engineers to support system authorization and continued operation. This position offers the opportunity to build practical security capabilities for disconnected engineering environments that support product development and testing.

Responsibilities

Harden Windows, Red Hat Enterprise Linux (RHEL), virtualization platforms, and network infrastructure. Apply Defense Information Systems Agency Security Technical Implementation Guides (DISA STIGs), implement approved access and network-segmentation controls, and test changes with IT engineers to preserve required services.
Configure and maintain security information and event management (SIEM), endpoint protection, and centralized logging. Integrate log sources, tune alerts, verify agent and data-collection health, and support investigation, containment, and recovery when security events occur.
Assess vulnerabilities and security configurations, prioritize findings with system owners, implement approved fixes, and verify results. Document remaining risks and maintain security tools, patches, and update content through approved offline processes.
Work with the ISSM and ISSO on Risk Management Framework (RMF) activities to obtain and maintain an Authorization to Operate (ATO). Provide configuration records, scan results, system diagrams, control-implementation evidence, and remediation updates for assessments and Plans of Action and Milestones (POA&Ms).
Review internally developed software, third-party packages, and container images with developers before introduction into classified systems. Support controlled testing and release, automate repeatable security checks, and maintain operating procedures and change records.

Basic Qualifications

Hands-on experience supporting classified information systems, including work within approved security boundaries and controlled change processes.
Experience securing Windows and Linux servers or workstations, including authentication, permissions, auditing, and services; working knowledge of Active Directory and Group Policy.
Experience hardening networks through segmentation, firewall or access-control rules, secure management interfaces, and restriction of unnecessary ports, protocols, and services.
Practical experience applying DISA STIGs, assessing configurations through automated and manual checks, documenting findings, and verifying corrective actions.
Experience configuring or maintaining a SIEM, including log collection, searches, alert tuning, and investigation.
Experience deploying or administering endpoint protection, including policy configuration, agent health, update management, approved exclusions, and troubleshooting.
Experience using vulnerability-assessment tools to identify findings, evaluate operational impact, and confirm remediation.
Experience supporting ISSM/ISSO authorization activities, security-control evidence, assessment preparation, and finding closure under the RMF.
Ability to troubleshoot security configurations, document work clearly, and explain technical risks and proposed fixes to security and IT teams.
Experience performing privileged administration on secure or classified systems, including administrative account management, access controls, audit logging, and documented configuration changes.
Must possess and maintain a current cybersecurity certification accepted for the position’s assigned DoD Cyber Workforce Framework (DCWF) work role and proficiency level, and meet applicable DoD 8140.03 and program qualification requirements.

Preferred Skills and Experience

Experience maintaining air-gapped systems, including approved media transfers, offline patches, security-content updates, and local software repositories.
Experience with Splunk or Elastic Security, including Linux rsyslog, Windows event forwarding, or similar log collection methods.
Experience with Trellix endpoint protection, ePolicy Orchestrator (ePO), or data loss prevention (DLP); Nessus/Tenable; or Security Content Automation Protocol (SCAP) assessment tools and STIG Viewer. Equivalent tool experience is relevant.
Experience securing VMware vSphere/ESXi or Microsoft Hyper-V, storage and backup services, and Juniper or comparable network infrastructure.
Experience with PowerShell, Bash, Python, or Ansible to automate configuration checks, evidence collection, or approved remediation.
Experience with eMASS or comparable authorization-documentation tools, initial system authorization, and applicable NIST security controls, Defense Counterintelligence and Security Agency (DCSA) requirements, or the Joint Special Access Program Implementation Guide (JSIG).
Experience reviewing software dependencies, container images, and software bills of materials (component inventories), using tools such as Trivy, Anchore, or equivalent. Familiarity with approved on-premises source-control and build/release workflows, such as GitHub Enterprise Server.

Additional Requirements

Ability to put in extended hours, including evenings and weekends, when required to meet aggressive timelines.
This role is based in Torrance, CA and requires full-time onsite presence.
Occasional travel is required.

Physical Demands

Ability to lift and move equipment weighing at least 40 pounds when supporting equipment installation or maintenance, with or without reasonable accommodation.

Other Duties

Please note this job description is not designed to cover or contain a comprehensive listing of activities, duties or responsibilities that are required of the employee for this job. Duties, responsibilities and activities may change at any time with or without notice.

Benefits and Perks

All full-time employees are granted meaningful long-term equity, sharing in the company’s significant growth trajectory. We offer four (4) weeks of paid time off, ten (10) company-paid holidays, and comprehensive health benefits - including 100% employee-covered medical and strong dependent coverage, along with dental and vision plans. We also provide paid parental leave to support growing families, a $100 monthly fitness stipend to promote health and performance, and onsite EV charging for convenience. In addition, employees enjoy perks like catered meals, company-covered food during high-demand periods, and a fully stocked kitchen to stay fueled throughout the day.

Security Clearance and Access

U.S. citizenship is required. Must possess and maintain an active Top Secret/Sensitive Compartmented Information (TS/SCI) security clearance and meet applicable program-access requirements. This position requires privileged access to classified systems. Required privileged-user training and system-specific authorizations must be completed before performing privileged duties. Castelion offers a generous benefits package. Please refer to the bottom of our Careers page for more details.

Other Duties

Additional Eligibility Requirements

This position may require access to classified information or restricted U.S. Government sites, systems, or information, as determined by the Company and/or applicable U.S. Government requirements. If the position is so designated, your employment in the role may be contingent upon your ability to obtain and maintain the required U.S. Government security clearance or other government authorization, and to satisfy any citizenship or other eligibility requirements imposed by applicable law, regulation, executive order, or government contract requirements. You will be notified if and when such requirements apply.

Affirmative Action/EEO Statement

Castelion is an Equal Opportunity Employer. We are committed to providing equal employment opportunities to all applicants and employees without regard to race, color, religion, sex, sexual orientation, gender identity, national origin, age, disability, genetic information, protected veteran status, or any other characteristic protected by applicable federal, state, or local law.

Castelion is committed to providing reasonable accommodations to qualified individuals with disabilities throughout the application and hiring process. If you require a reasonable accommodation to complete an application, participate in the interview process, or otherwise participate in the hiring process, please contact hr@castelion.com. Requests for accommodation will be considered on an individual basis and handled in accordance with applicable law.

Castelion is committed to fostering a workplace where employment decisions are based on qualifications, business needs, and the ability to perform the essential functions of the role, with or without reasonable accommodation.

EAR/ITAR Requirements

This position requires access to export-controlled information, and as such, employment (or hiring of a contractor) is contingent upon the candidate’s ability to access all applicable export-controlled information without additional export licensing being required by the Bureau of Industry and Security and/or the Directorate of Defense Trade Controls.

Apply on job-boards.greenhouse.io About employer

More about this job

Skills

Security regulations
Microsoft Windows
Red Hat Enterprise Linux
Event planning
Symantec Endpoint Protection
Risk management
Linux
Auditing
Microsoft Active Directory
Troubleshooting
Troubleshoot
Cybersecurity
Splunk
Loss prevention
Nessus
VMware
Microsoft PowerShell
Bash
Python
Ansible
eMASS
Documentation
GitHub

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Jobs in the United States