Microsoft 365 Security & Identity Admin

System One, Inc.; Reston (VA); On-site; USD 95,000 - 130,000; Full time

Job summary

System One, Inc. is seeking a Microsoft Systems Administrator to support, secure, and optimize Microsoft 365 environments. The role focuses on administration of O365, email security, identity management, and endpoint security across the organization.

Ideal candidates will have hands-on experience with Intune, Defender, Purview, Entra ID, and Exchange Online, plus a background in IAM and cloud services. The position is in Reston, VA and emphasizes security, compliance, and cross‑team

Qualifications

• Experience administering Microsoft 365 environments.
• Hands-on experience with: Microsoft Intune, Defender, Purview, Conditional Access, Entra ID, Exchange Online.
• Experience managing Windows desktop environments and Microsoft cloud services.
• Knowledge of IAM, endpoint security, and security best practices.
• Experience with Mimecast, Azure, or Windows Server administration.
• Experience supporting public sector, government, or regulated environments and knowledge of NIST, or other compliance frameworks.
• Microsoft certifications such as Microsoft 365 Administrator, Endpoint Administrator, Identity and Access Administrator, Security Operations Analyst or Azure Administrator.

Responsibilities

• Configure and maintain Conditional Access Policies, multifactor authentication, and access controls.
• Administer Microsoft Intune for endpoint management, device compliance, application deployment, and updates.
• Monitor and manage Microsoft Defender security alerts and respond to security-related incidents.
• Support Microsoft Purview policies, including data protection, retention, and compliance requirements.
• Manage email security, respond to threats, and remediate vulnerabilities.
• Manage Windows endpoints and assist with Windows Server administration.
• Perform system monitoring, patch management, and vulnerability remediation.
• Maintain technical documentation and support IT projects and initiatives.
• Work with internal teams and vendors to ensure reliable and secure technology services.

Skills

Microsoft 365 administration

Identity and Access Management

Endpoint management

Security best practices

Public sector experience

Tools

Intune

Defender

Purview

Entra ID / Azure AD

Exchange Online

Mimecast

Azure

Windows Server

Job description

System One, Inc. is seeking a Microsoft Systems Administrator to support, secure, and optimize Microsoft 365 environments. The role focuses on administration of O365, email security, identity management, and endpoint security across the organization.

Ideal candidates will have hands-on experience with Intune, Defender, Purview, Entra ID, and Exchange Online, plus a background in IAM and cloud services. The position is in Reston, VA and emphasizes security, compliance, and cross‑team