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.

Senior Cybersecurity Architect

We are seeking a Senior Cybersecurity Architect to lead the design and implementation of secure, resilient information security systems, monitoring, red/blue team activities, and more in support of regulated, compliance-heavy environments. This hands-on role is responsible for translating mission, system, and regulatory requirements into end-to-end cybersecurity solutions. These complete solutions should benefit from the candidate's experienced and thoughtful implementation of company policy, automation and enforcement of workflows/processes, and technical security measures.

Based in our Torrance, CA HQ, you'll lead efforts to build, maintain, and continuously improve our security and compliance posture across both local and remote sites. You'll collaborate with cross-functional teams—including IT, software development, operations, engineering, manufacturing, and legal—to ensure our security controls meet both technical and regulatory standards.

The ideal candidate brings deep technical expertise, strong systems thinking, hands-on experience, and is well-versed in frameworks like NIST SP 800-171, CMMC, or ISO 27001.

If you love solving hard problems under strict rules, thrive in high-stakes environments, and believe security should be a business enabler—not a blocker—this role is for you.

Responsibilities

Define and implement security architectures aligned with Zero Trust principles, defense-in-depth, and least-privilege models
Develop security reference architectures, patterns, and standards for enterprise and program-level systems
Ensure cybersecurity is embedded across the full system lifecycle (requirements, design, development, test, deployment, sustainment)
Design, implement, and maintain cybersecurity tools and systems, including firewalls, EDR, IDS/IPS, SIEM, and vulnerability scanners.
Conduct threat modeling, security risk assessments, and vulnerability analyses.
Proactively monitor security events, investigate suspicious activity, and respond to incidents with urgency and precision.
Develop and maintain System Security Plans (SSPs), POA&Ms, and supporting documentation for audits and assessments.
Partner with IT, engineering, DevSecOps, and Program Security to integrate security into infrastructure and application design.
Manage security patching cycles and lead remediation efforts based on risk assessments.
Support audit, compliance, and risk management activities (e.g., NIST, CMMC, & others) and manage supply chain cybersecurity concerns.
Conduct regular internal audits and readiness checks in preparation for external audits or DoD reviews.
Serve as on-site cybersecurity expert for Torrance HQ and occasionally travel (5–10%) to other locations (TX/NM).

Required Qualifications

7-10+ years of hands-on experience in cybersecurity engineering, infrastructure security, or related fields.
Strong technical background in network security, endpoint protection, access control, and vulnerability management.
Proficiency with modern security tools (e.g., CrowdStrike, Palo Alto, Nessus, Splunk, Snort, etc.).
Experience with incident response, malware analysis, and penetration testing.
Demonstrated experience with cloud security (AWS, Azure, or GCP).
Deep understanding of security principles, threats, and frameworks (e.g., cyber kill chain, MITRE ATT&CK, NIST, CIS Controls).
Strong documentation, troubleshooting, and communication skills.
Ability to thrive in fast-paced, high-pressure environments with competing priorities.
Ability to pivot between analyst, threat hunter, and implementer roles with ease.
Eligibility to keep and maintain a U.S. security clearance.

Preferred Qualifications

Experience in regulated environments (DoD, aerospace, SCIFs).
Active Security+, CISSP, CISM, CEH, or similar senior-level certification(s).
Relevant experience with NIST 800-171, CMMC, DFARS, or other in relation to cybersecurity audit readiness.
Experience with incident response, malware analysis, or penetration testing is a plus.
Experience in SOC operations.

Castelion offers a generous benefits package. Please refer to the bottom of our Careers page for more details.

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.

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.