Senior Information System Security Engineer (ISSE)

Vista Global Solutions (VGS) is seeking a Senior Information System Security Engineer (ISSE) to support the migration and enterprise implementation of Microsoft Defender across Windows, macOS, and Linux environments at the Uniformed Services University of the Health Sciences (USUHS).
The Senior ISSE will serve as a key cybersecurity engineering and compliance resource responsible for ensuring Microsoft Defender configurations, endpoint security controls, and transition activities align with Department of Defense (DoD) cybersecurity requirements and applicable Defense Information Systems Agency (DISA) Security Technical Implementation Guides (STIGs).
What You’ll Do:

Perform STIG assessments, security hardening, and compliance validation for Microsoft Defender tenant configurations and Windows, macOS, and Linux endpoints.
Conduct Security Content Automation Protocol (SCAP) scans and manual configuration reviews to validate DISA STIG compliance.
Develop and maintain STIG Compliance Checklists and supporting security documentation required for enterprise deployment.
Identify security findings, recommend corrective actions, and coordinate remediation to achieve required compliance thresholds, including resolution of Category I findings.
Validate endpoint security safeguards before removal of legacy Trellix components, including BitLocker and FileVault encryption and associated key escrow.
Verify security audit and telemetry integration with Splunk Security Information and Event Management (SIEM) and Microsoft Sentinel.
Review security exceptions, deployment variances, and enclave-specific requirements and assess associated cybersecurity risks.
Support the Risk Management Framework (RMF) lifecycle, including development, maintenance, and submission of Assessment & Authorization (A&A) artifacts and Authorization to Operate (ATO) documentation within eMASS.
Perform vulnerability assessments and patch-compliance verification using Assured Compliance Assessment Solution (ACAS).
Develop, maintain, and track Plans of Action and Milestones (POA&Ms) through remediation and closure.
Coordinate with cybersecurity, endpoint engineering, infrastructure, and operational stakeholders to ensure security requirements are incorporated throughout the Microsoft Defender transition.
Provide cybersecurity engineering recommendations and technical guidance to program leadership and Government stakeholders.

What You Bring:
Required:

Minimum 5 years of cybersecurity engineering, information assurance, or security compliance experience, preferably supporting Federal or DoD environments.
Active DoD Secret security clearance required.
Current DoD IAT Level II-compliant certification, such as Security+ CE, CySA+, or GSEC, as applicable to current DoD requirements.
Demonstrated experience implementing or assessing DISA STIGs and DoD cybersecurity requirements.
Experience with vulnerability assessment, remediation tracking, and security configuration validation.
Working knowledge of the DoD Risk Management Framework (RMF) and A&A processes.
Experience developing or maintaining cybersecurity documentation, including STIG checklists, POA&Ms, security control evidence, and ATO artifacts.
Experience with enterprise endpoint security technologies and Windows endpoint security controls.
Knowledge of encryption technologies and key-management concepts, including BitLocker and FileVault.
Ability to analyze technical security findings and communicate risks and remediation recommendations to technical and non-technical stakeholders.

Preferred:

Advanced cybersecurity certification such as CISSP, CISM, or CASP+/SecurityX, as applicable.
Microsoft security certification relevant to Microsoft Defender, Microsoft 365, or security operations.
Experience with Microsoft Defender security technologies.
Experience with DISA STIGs, STIG Viewer, and SCAP compliance tools.
Experience with ACAS, eMASS, RMF, and A&A processes.
Experience with Splunk SIEM and/or Microsoft Sentinel.
Experience with BitLocker and FileVault.
Experience with Trellix/ePO environments.
Experience supporting Windows, macOS, and Linux endpoint security.
Experience developing and tracking POA&Ms through remediation and closure.

What We Offer:
VGS offers a competitive benefits package to include: paid holidays, paid time off including sick and vacation leave, medical, dental and vision insurance, flexible spending accounts, short and long term disability, company paid life insurance, 401(k) with a company match and discretionary profit sharing and tuition reimbursement.