About the Role
We are seeking a hands-on Systems Administrator to support a mixed Windows, Linux, virtualization, networking, Microsoft 365, and cybersecurity environment. This role combines production systems administration with onsite user support and requires the ability to troubleshoot across workstations, servers, identity, networks, VPNs, and security tooling.
Requirements
Key Responsibilities:
Administer Windows Server, Active Directory, Group Policy, DNS, DHCP, permissions, and routine identity lifecycle tasks.
Manage VMware vSphere/ESXi, Linux servers, virtual machines, storage, patching, backups, certificates, logs, and service troubleshooting.
Configure and support pfSense, OpenVPN, Cisco and UniFi switching, VLANs, routing, NAT, firewall policy, wireless, and network segmentation.
Administer the primary Microsoft 365 tenant and smaller tenants, including Entra ID, Exchange Online, Teams, SharePoint, licensing, MFA, and Conditional Access.
Triage and investigate Microsoft Defender XDR and Sentinel alerts; collect evidence, contain, remediate, document, or escalate incidents.
Manage and security-monitor the CUI environment, including access control, logging, vulnerability remediation, configuration management, and compliance evidence.
Provide onsite helpdesk support, workstation deployment, onboarding/offboarding, cabling, hardware replacement, and equipment inventory.
Support GitLab and development infrastructure, including access, availability, backups, certificates, and basic service troubleshooting.
Qualifications:
3+ years of hands-on systems administration or advanced infrastructure support experience in production environments.
Strong TCP/IP, DNS, DHCP, subnetting, routing, VLAN, NAT, VPN, firewall, Windows/AD, Linux, and virtualization fundamentals.
Experience administering Microsoft 365; Microsoft security operations experience is strongly preferred.
Demonstrated ability to troubleshoot independently, document changes, validate results, and use safe rollback procedures.
Ability to work onsite, perform physical IT support, and handle CUI and sensitive information under applicable requirements.
Preferred Experience:
Direct experience with pfSense, OpenVPN, Cisco, UniFi, VMware vSphere, and GitLab.
Experience with Microsoft Entra ID, Conditional Access, Intune, Exchange Online, Defender XDR, Sentinel, and KQL.
Experience supporting segmented, regulated, government-contractor, defense-industry, or other security-sensitive environments.
Working knowledge of CUI, CMMC Level 2, NIST SP 800-171, DFARS 252.204-7012, access-control evidence, and compliance documentation.
Experience maintaining system security plans, configuration baselines, inventories, diagrams, remediation records, and audit evidence.
PowerShell, Bash, Python, or other scripting and automation experience.
Relevant certifications such as Security+, Network+, CCNA, Microsoft, VMware, or Linux certifications, or equivalent demonstrated experience.
About Def-Logix, Inc.
Def-Logix, Inc. is an 8(a)-certified, Veteran-Owned Small Business headquartered in San Antonio, Texas. We specialize in cutting-edge cybersecurity research and development, including offensive and defensive cyber capabilities, custom software engineering, and AI-driven solutions. Our clients include government agencies, defense contractors, and enterprise organizations seeking advanced, tailored cybersecurity solutions.