Senior Cybersecurity Analyst

About the role

About Castelion

Castelion is moving incredibly fast to develop and deliver advanced defense systems at a time when execution matters more than ever. We believe focus and technical excellence are decisive advantages – and we are building a team that can deliver real capability, not just concepts.

This is a rare opportunity to join at an early stage, where your work will directly shape critical systems, influence major technical decisions, and have immediate, real-world impact.

Senior Cybersecurity Analyst

We are seeking an experienced Senior Cybersecurity Analyst to join our team. This role will be responsible for protecting sensitive systems, data, and infrastructure critical to national security. The ideal candidate will have expertise in threat detection, SOC operations, incident response, and compliance frameworks specific to the defense industrial base.

Responsibilities

Lead 24/7 security monitoring efforts using SIEM platforms and advanced threat detection tools

Analyze security events, identify potential threats, and coordinate incident response activities

Identify vulnerabilities and recommend remediation strategies for complex environments

Analyze malware, APT tactics, and threat actor behavior

Perform threat hunting activities to proactively identify sophisticated adversaries

Conduct forensic analysis of security incidents involving classified and sensitive systems

Contribute to compliance with NIST 800-171, CMMC, DFARS, ITAR, and other DoD requirements

Contribute to and/or maintain security documentation including internal documentation, policies and procedures, incident reports, and audit artifacts

Configure and maintain security tools including IDS/IPS, EDR, DLP, and vulnerability scanners

Support secure architecture reviews across the organization

Mentor junior analysts and contribute to team skill development

Coordinate with IT, engineering, manufacturing, and program teams on security initiatives

Participate in threat intelligence sharing with government and industry partners

Basic Qualifications

3+ years of experience in cybersecurity, information security, or related technical security roles

Hands-on experience with security operations, incident response, and threat analysis

Expert knowledge of security tools: SIEM (Splunk, QRadar, Sentinel), EDR (CrowdStrike, Carbon Black), IDS/IPS

Deep knowledge of MITRE ATT&CK framework and adversary tactics, techniques, and procedures

Familiarity with threat intelligence platforms and OSINT techniques

Experience protecting Controlled Unclassified Information (CUI)

Experience operating within aerospace, defense, national security, government contracting, or highly regulated technical environments

Strong understanding of network protocols, operating systems (Windows, Linux), and cloud environments

Experience as a member of incident response protocols, vulnerability management, and security operations functions

Proficiency in scripting/automation

U.S. Person status required to comply with ITAR regulations

Ability to obtain and maintain a U.S. security clearance

Preferred Skills and Experience

Experience supporting defense manufacturing or operational technology (OT/ICS) environments

Experience securing embedded systems, avionics, autonomous systems, or weapon systems

Experience at high-growth startups or scaling organizations

Hands-on experience implementing SIEM and SOAR operations

Experience with CMMC 2.0, NIST SP 800-171, DFARS 252.204-7012/7020/7021, ITAR, and related defense compliance requirements

Industry certifications such as Security+, CEH, CISA, GIAC, or equivalent

Degree in Cybersecurity, Computer Science, Engineering, or related field

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

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.

Affirmative Action/EEO Statement

Employment with Castelion is governed on the basis of competence and qualifications and will not be influenced in any manner by race, color, religion, gender, national origin/ethnicity, veteran status, disability status, age, sexual orientation, gender identity, marital status, mental or physical disability or any other legally protected status.

ITAR Requirements

To conform to U.S. Government export regulations, applicant must be a (i) U.S. citizen or national, (ii) U.S. lawful, permanent resident (aka green card holder), (iii) Refugee under 8 U.S.C. § 1157, or (iv) Asylee under 8 U.S.C. § 1158, or be eligible to obtain the required authorizations from the U.S. Department of State.