Information System Security Engineer

Job Description

Role: Information System Security Engineer (ISSE)

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Location: Fairfax, VA or Denver, CO

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Salary: $150,000 - $210,000 plus 50% employer package

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Security Clearance: Active TS/SCI with CI Polygraph Required

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We are working with an established organization supporting mission-critical programmes across the US Defense and Intelligence Community, who are looking to appoint an experienced Information System Security Engineer (ISSE) to join their technical security team in Fairfax, VA or Denver, CO.

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This opportunity is suited to a technically proficient Security Engineer with extensive experience in ICD-503, Risk Management Framework (RMF), Assessment & Authorization (A&A), and Authority to Operate (ATO) processes, alongside a strong working knowledge of Linux-based infrastructure.

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You will play a key role in implementing security controls, maintaining accreditation, and ensuring compliance across complex, mission-critical environments.

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The position requires someone who can bridge the gap between cybersecurity compliance requirements and practical technical implementation, with the ability to understand, assess, and secure enterprise Linux systems.

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Key Responsibilities

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• Lead and support ICD-503 Risk Management Framework (RMF) activities, including Assessment & Authorization (A&A) and ongoing ATO maintenance.
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• Develop, review, and maintain System Security Plans (SSPs), security control assessments, POA&Ms, and supporting accreditation documentation.
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• Implement and maintain security controls across complex Linux-based infrastructure, including virtualized and bare-metal environments.
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• Conduct vulnerability assessments, compliance scanning, security audits, and continuous monitoring activities.
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• Work closely with Systems Administrators and Engineering teams to identify, remediate, and mitigate security vulnerabilities.
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• Support system hardening, patch management, configuration management, and audit log reviews.
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• Evaluate proposed system architectures and provide technical security guidance to ensure compliance with Intelligence Community requirements.
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• Coordinate security assessments, remediation activities, and risk management processes throughout the system lifecycle.
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• Collaborate with development and infrastructure teams to integrate security requirements into system design and operational processes.
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• Maintain compliance with applicable DoD and Intelligence Community cybersecurity policies and standards.
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Required Skills & Experience

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• Active TS/SCI clearance with CI Polygraph, required.
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• 10+ years of relevant experience in Information Systems Security Engineering, Information Assurance, or cybersecurity engineering.
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• Extensive experience with ICD-503, including security accreditation, compliance documentation, and control implementation.
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• Strong understanding of Risk Management Framework (RMF), Assessment & Authorization (A&A), and Authority to Operate (ATO) processes.
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• Solid technical knowledge of Linux/Unix environments, ideally with previous hands-on Linux Systems Administration or Engineering experience.
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• Experience developing and maintaining System Security Plans (SSPs), POA&Ms, and security assessment documentation.
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• Knowledge of vulnerability management, continuous monitoring, security scanning, and remediation processes.
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• Familiarity with NIST security frameworks, including NIST SP 800-37 and associated security controls.
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• CompTIA Security+ CE certification or higher-level equivalent.
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Desirable Skills & Experience

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• Bachelor's Degree in Computer Science, Information Technology, Cybersecurity, Engineering, or a related technical discipline, highly preferred.
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• Experience with Red Hat Enterprise Linux (RHEL) and enterprise Linux system administration.
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• Exposure to cloud infrastructure, particularly AWS and cloud security architectures.
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• Familiarity with Kubernetes, Docker, and containerised environments.
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• Experience with infrastructure automation and configuration management tools, particularly Ansible, Puppet, or Foreman.
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• Knowledge of vulnerability scanning tools including Nessus, Nmap, and Rapid7.
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• Familiarity with VMware, virtualisation technologies, and enterprise infrastructure.
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• Experience with Linux scripting, Bash, and system automation.
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Benefits Package

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• Competitive base salary, dependent on experience and education.
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• Generous 401(k) retirement contributions (25%).
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• Individual Benefits Account (IBA), providing additional flexibility towards benefits and paid time off.
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• Comprehensive medical, dental, and vision coverage.
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• Generous paid time off, with opportunities for up to 8 weeks depending on individual arrangements.
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• Life insurance coverage.
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• 100% tuition reimbursement for eligible educational programmes.
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• Flexible working hours within a fully on-site environment.
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We welcome applications from experienced Information System Security Engineers with a strong technical foundation who are looking to contribute to complex, security-critical programmes.

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Apply today for a confidential discussion about the opportunity.