Senior Cybersecurity Architect

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.

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.

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.

• 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, Dev Sec Ops , 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).

• 7-10+ years of hands‑on experience in cybersecurity engineering, infrastructure security, or related fields.
• Strong technical background in…