Senior Microsoft O365 Security Engineer & SME

Job Title: Senior Microsoft 365 Security Engineer & Subject Matter Expert (SME)
Role Type: Contract
Role Duration: 6 Months + good chance of extensions
Location: Washington, DC
Work Model: Hybrid – 1 day onsite per week (potentially remote pending approval)
Clearance Requirement: Ability to obtain Public Trust

Job Summary
We are seeking a Senior Microsoft 365 Security Engineer & Subject Matter Expert (SME) to lead the design, implementation, and optimization of Microsoft 365 security solutions across complex IT/OT environments. This role requires deep hands?on expertise with the Microsoft 365 security ecosystem, including Defender, Purview, Entra, and Intune, as well as the ability to provide technical leadership, risk assessment, and strategic guidance across enterprise environments.
The ideal candidate brings strong architectural experience, a security first mindset, and the ability to collaborate with cross functional technical and security teams to deliver compliant, scalable, and resilient M365 security solutions.

Primary Responsibilities

• Provide strategic guidance, oversight, and technical leadership for M365 application deployments across IT/OT environments
• Implement and manage security solutions and compliance controls across a multi tenant Microsoft 365 ecosystem (Defender, Purview, Entra, Intune, OneDrive, SharePoint, Teams)
• Serve as a technical SME for Microsoft Defender (EDR & Email Security) and Microsoft Purview (DLP, Compliance, Governance) initiatives
  • Develop and implement Defender and Purview strategies across on?premises and cloud environments (Azure & AWS)
  • Architect, design, and enhance Defender and Purview solutions and technologies
  • Perform risk assessments to identify gaps in security coverage
  • Research emerging threats, trends, and evasion techniques related to the M365 security stack
• Interface with internal stakeholders and facilitate technical working group and interchange meetings
• Develop technical artifacts supporting M365 deployments, including requirements, architecture, test plans/scripts, and implementation plans
• Collaborate with cross functional teams including Program/Project Management, M365 administrators, Data Center, End User Services, Security Engineering, SOC, Compliance, and System Owners
• Apply systems and software development lifecycle best practices throughout design, testing, and implementation
• Coordinate with vendors and conduct analyses of alternatives (AoA) to evaluate M365 security solutions and support proof of concept efforts
• Develop scope, cost estimates, and implementation schedules for M365 initiatives
• Participate in business continuity and IT disaster recovery planning

• Ability to obtain a Public Trust clearance
• 10+ years of experience providing technical leadership, guidance, and oversight for M365 security administration and deployments
• Strong hands on experience designing and implementing end to end M365 security solutions across on premises, hybrid, and cloud IT/OT environments
• Deep knowledge of Microsoft 365 security architecture and tools, including Defender, Purview, Entra, Intune, Sentinel, SharePoint, and Teams
• Experience using Microsoft Purview for data governance, DLP policy implementation, and eDiscovery
• Experience using Microsoft Intune for GPO and endpoint policy management
• Experience deploying and managing Microsoft Defender for threat protection
• Experience configuring Entra ID for identity and access management
• Strong understanding of compliance requirements and security frameworks (NIST, ISO 27001, SOC 2)
• Knowledge of threat vectors, vulnerabilities, risk assessment, and incident detection and response
• Proficiency in PowerShell
• Strong documentation skills, including technical reports, procedures, and architecture diagrams
• Excellent analytical, communication, and presentation skills
• Ability to work independently and collaboratively in a cross functional environment

• Microsoft 365 Administrator certifications such as MS102 or MS900

• Bachelor of Science in Information Technology, Computer Science, or an engineering?related discipline
• 10 years of prior relevant experience

System One, and its subsidiaries including Joulé and Mountain Ltd., are leaders in delivering outsourced services and workforce solutions across North America. We help clients get work done more efficiently and economically, without compromising quality. System One not only serves as a valued partner for our clients, but we offer eligible employees health and welfare benefits coverage options including medical, dental, vision, spending accounts, life insurance, voluntary plans, as well as participation in a 401(k) plan.

System One is an Equal Opportunity Employer. All qualified applicants will receive consideration for employment without regard to race, color, religion, sex (including pregnancy, childbirth, or related medical conditions), sexual orientation, gender identity, age, national origin, disability, family care or medical leave status, genetic information, veteran status, marital status, or any other characteristic protected by applicable federal, state, or local law.

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