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Systems Security Engineer Senior

Modern Technology Solutions, Inc.
$200,000.00 - $240,000.00 / yr
401(k)
United States, California, El Segundo
Jan 22, 2026
Modern Technology Solutions Inc. (MTSI) is seeking a highly experienced Systems Security Engineer to support the United States Space Force (USSF) organization that is responsible for developing software and the supporting architecture for the organize, understand, plan, decide, direct, and monitor capabilities within the C2 Joint Capability Areas (JCAs).
In this role, you will accomplish the integrated technical management and application methods, processes, and tools to deliver systems that satisfy stakeholder security needs for operation in contested environments.
Job responsibilities will include, but may not be limited to:
  • Provide technical knowledge and analysis of complex problems that need knowledge of current best practices and Government mandated policies for effective development and implementation of systems security solutions
  • Comprehensive assessments of system cyber security architecture, security events/activities and posture
  • Develop and implement system security plans, policies, and controls in accordance with DoD and NIST standards (e.g., RMF, NIST SP 800-53)
  • Conduct security risk and vulnerability assessments and develop mitigation strategies
  • Provide system security expertise to obtain and maintain the Authorization to Operate (ATO) Risk Management Framework (RMF) accreditation requirements
  • Develop and conduct processes for verification of Interim Authority To Test (IATT) and Interim Authority to Connect (IATC) documentation and procedures for prototypes and external systems connecting to the Space C2 Enterprise
  • Support efforts to accredit software systems for IL4 and up to and including TS/SCI/SAP environments within OEM or government developed cloud environments as directed by the government
  • Coordinate with cross-functional teams to ensure systems security is integrated early in the systems engineering process
  • Contribute to Program Protection Plans (PPPs), Security Classification Guides (SCGs), and related security documentation
  • Provide technical expertise in areas that have system security and/or cybersecurity touch points such as defensive cyberspace operations, joint operations planning, policy, and technical intelligence
  • Initiate actions for providing support to various working groups such as system security working groups, cybersecurity working groups, change management boards, etc.
Qualifications
Required Experience:
  • 20+ years of professional experience supporting the DoD and/or IC communities
  • 5+ years of experience in cybersecurity or systems security engineering within a DoD environment
  • Experience supporting system accreditation packages and security documentation
  • Familiarity with RMF, NIST SP 800 series, and DoDI 8510.01
  • Demonstrated experience with applicable IC and DoD policies, procedures, and operating instructions related to program security, information assurance, Experience working closely with ISSMs/ISSEs and government security stakeholders
  • At least 2 years of TS/SCI experience
Desired Experience:
  • Relevant experience and knowledge of Defensive Cyber Operations (DCO)
  • Experience within the National Security Space and/or the Ground Systems Mission Areas
  • Experience with SDA SW
  • Experience with Infrastructure, Platforms, Networks and Data
Education /Certification Requirements:
  • B.S. in related field
  • M.S. in related field
Security Clearance Level Required:
  • Active TS/SCI (Must be a U.S. Citizen)
Location/Travel Requirements:
  • Place of work is El Segundo, CA - Hybrid (on-site/telework)
  • May require travel up to 25% of time within the continental United States
The pay range for this position in California is $200,000/year to $240,000/year; however, base pay offered may vary depending on established government contract rates, job-related knowledge, skills, and experience, and other factors. MTSI also offers a full range of medical, financial, and other benefits, dependent on the position offered. This information is provided per the Colorado Equal Pay Act. Base pay information is based on market location. Applicants should apply via MTSI's internal or external careers site
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  • Interesting Work:



    Our co-workers support some of the most important and critical programs to our national defense and security.






  • Values:



    Our first core value is that employees come first. We challenge our co-workers to provide the highest level of support and service, and reward them with some of the best benefits in the industry.






  • 100% Employee Owned:



    We have a stake in each other's success, and the success of our customers. It's also nice to know what's going on across the company; we have company wide town-hall meetings three times a year.






  • Great Benefits - Most Full-Time Staff Are Eligible for:





    • Starting PTO accrual of 20 days PTO/year + 10 holidays/year


    • Flexible schedules


    • 6% 401k match with immediate vesting up to $9k annually


    • Semi-annual bonus eligibility (July and December)


    • Company funded Employee Stock Ownership Plan (ESOP) - a separate qualified retirement account


    • Up to $10,000 in annual educational reimbursement


    • Other company funded benefits, like life and disability insurance


    • Optional zero deductible Blue Cross/Blue Shield health insurance plan







  • Track Record of Success:



    We have grown every year since our founding in 1993.




Modern Technology Solutions, Inc. (MTSI) is a 100% employee-owned engineering services and solutions company that provides high-demand technical expertise in Digital Transformation, Modeling and Simulation, Rapid Capability Development, Test and Evaluation, Artificial Intelligence, Autonomy, Cybersecurity and Mission Assurance

MTSI delivers capabilities to solve problems of global importance. Founded in 1993, MTSI today has employees at over 20 offices and field sites worldwide.

For more information about MTSI, please visit www.mtsi-va.com

MTSI embraces nine core values including our first core value of Employees come first. Consistent with our Core Values, we are committed to Equal Opportunity, making decisions without regard to race, color, religion, sex, national origin, age, military/veteran status, disability, or any other characteristics protected by applicable law. MTSI is committed to Equal Employment Opportunity and providing reasonable accommodations to applicants and employees with physical and/or mental disabilities.


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