Systems Engineer III

Reflexive Concepts; Fort Meade (MD); On-site; USD 110,000 - 170,000; Full time

Job summary

Reflexive Concepts is seeking a skilled Systems Engineer III to join our team and lead engineering for the NSA's Enterprise Endpoint Detection and Response program. This senior role demands deep expertise in endpoint security architectures and cross-domain integration.

You will design, deploy, and optimize Microsoft Defender for Endpoint and Trellix HX across hybrid on‑premises, cloud, and VDI environments, ensuring robust visibility and threat containment.

Qualifications

• 20 years of experience in systems engineering or similar roles.
• Bachelor's Degree in Computer Science or a related field.
• Strong knowledge of endpoint security architectures and operating systems.
• DoD 8570/8140 IAM Level II or III baseline certifications.

Responsibilities

• Lead lifecycle engineering and scale of MDE and Trellix HX across hybrid environments.
• Author complex system engineering and implementation plans.
• Tune agent configurations and exclusion policies to minimize mission friction.
• Develop and implement IOCs with threat intelligence using KQL/YARA.
• Mentor junior and mid-level engineers within the program.
• Provide advanced forensic support during critical incidents.

Skills

MDE architecture

Trellix HX

OS forensics

DoD IAM II/III

Education

Bachelor's Degree in CS or related field

Tools

MBSE

Cameo

Jira/Confluence

Job description

Reflexive Concepts is seeking a skilled Systems Engineer III to join our team!

Qualifications:

• Twenty (20) years of experience supporting projects and programs similar in scope and complexity
• Bachelors Degree in Computer Science or a related field

Duties and Responsibilities:

• The Senior Systems Engineer (Level 3) serves as a principal technical leader and subject matter expert within the National Security Agency's Enterprise Endpoint Detection and Response (EDR) Program. Operating in a highly classified, multi-domain infrastructure, the successful candidate will drive the strategic architectural design, end-to-end integration, deployment, and optimization of premier endpoint security platforms, specifically Microsoft Defender for Endpoint (MDE) and Trellix HX. This critical role bridges high-level systems architecture with operational defense capabilities, ensuring total endpoint visibility, robust threat containment, and resilient configuration management across all enterprise and mission-critical assets to defend national security infrastructure against sophisticated cyber threats.
• Lead the lifecycle engineering and scale-out architecture of MDE and Trellix HX across hybrid environments, including on-premises, cloud, and virtual desktop infrastructures (VDI), to include authoring complex system engineering and implementation plans, tuning agent configurations and exclusion policies to eliminate mission friction, and monitoring overall endpoint health at scale
• Collaborate closely with threat hunting and intelligence analysts to translate actionable threat intelligence into custom technical indicators of compromise (IOCs), utilizing Kusto Query Language (KQL) and YARA rules
• Act as a primary technical advisor to Government stakeholders on system risks and engineering considerations
• Provide advanced forensic support to the SOC during critical high-priority incidents
• Actively mentor junior and mid-level engineering personnel within the program

Required:

• Microsoft Defender for Endpoint (MDE) Expertise: proven engineering experience with MDE architecture, deployment strategies via MECM/SCCM or Intune, policy ring management, and advanced hunting using Kusto Query Language (KQL)
• Trellix HX Expertise: demonstrated experience engineering, deploying, and managing Trellix HX (formerly FireEye) controllers and agents within air-gapped or highly restricted networks, including the creation of OpenIOC and YARA rules
• Operating System & Forensic Knowledge: in-depth technical understanding of Windows, Linux, and macOS internals, including file systems, registry structures, and process execution mechanics
• Professional Standards: compliance with DoD 8570/8140 IAM Level II or III baseline certifications

Desired:

• Vendor Certifications: Microsoft Certified: Security Operations Analyst Associate (SC-200), Azure Security Engineer Associate (AZ-500), or Trellix Certified Engineering credentials
• Methodologies & Toolsets: experience with Model-Based Systems Engineering (MBSE), Cameo, and workflow management within the Atlassian Suite (Jira, Confluence)
• Technical Frameworks: familiarity with NSA Technical Manual Standards (e.g., NSA DS-89) and defense-in-depth engineering principles
• Core Competencies: strong record of team collaboration, exceptional transparency in managing high-consequence infrastructure, and an aptitude for developing technical leadership pipelines