JENNIFER O'SULLIVAN
Dublin
Summary
Senior Systems Engineer with extensive experience in delivering and securing enterprise infrastructure in diverse sectors. Proven track record in leading complex migrations, implementing robust security controls, and optimizing business-critical services using Microsoft 365 and Azure technologies.
Overview
21
21
years of professional experience
Work History
Senior Systems Engineer
Compass Informatics
Dublin
10.2023 - Current
- Lead engineer delivering network, security, infrastructure, Microsoft 365 and enterprise application solutions across public sector and commercial client environments.
- Led the design and migration from Cisco ASA firewalls to a FortiGate 100F high-availability platform, including firewall configuration, VPN, IPSec, HA configuration, migration validation, testing and troubleshooting; subsequently delivered the platform refresh to FortiGate 120G.
- Designed, implemented, and supported Azure and on-premises infrastructure, including Windows Server, Active Directory, Group Policy, Hyper-V, SCVMM, and SQL Server, facilitating seamless operations and user access.
- Administered Microsoft 365 and hybrid identity services as Global Administrator, including Entra ID, Exchange Online, Teams, SharePoint Online, OneDrive, directory synchronisation and endpoint management.
- Implement endpoint security controls using Microsoft Defender; perform vulnerability remediation, security hardening and patching activities supporting ISO 27001 readiness and wider cybersecurity requirements.
- Troubleshot complex infrastructure, networking, and authentication incidents across client and internal environments; developed PowerShell automation to enhance administrative processes and reporting accuracy.
- Design customer solutions, scope technical projects, present proposals and produce Statements of Work; work with vendors, clients and internal stakeholders through implementation, testing, change control and production support.
Systems Administrator
Compass Informatics
Dublin
06.2021 - 09.2023
- Managed hybrid Microsoft environments across Windows Server, Active Directory, Microsoft 365 and Azure-integrated services.
- Administered Exchange Online, SharePoint Online, Teams, Intune and SCCM for endpoint and service management.
- Supported infrastructure monitoring, patching, vulnerability remediation, backup and disaster recovery, and troubleshooting to ensure reliable service restoration.
- Contributed to cloud migration and infrastructure transformation projects, enhancing endpoint modernisation and enterprise application delivery.
IT Systems Administrator
Lafferty Architects
Dundrum
12.2016 - 05.2021
- Sole IT Administrator supporting approximately 60 users, with end-to-end responsibility for day-to-day IT operations, infrastructure, user support and business-critical systems.
- Administered Windows Server 2012/2016, Active Directory, Group Policy, Microsoft 365, SharePoint and core business systems.
- Managed SonicWall firewall and VPN access, backup and disaster-recovery systems, IT procurement, budgeting, supplier relationships, and infrastructure upgrade scheduling to ensure robust IT operations.
- Collaborated with senior management and third-party suppliers to ensure secure, reliable IT services, supporting telephony, meeting-room AV, and collaboration platforms.
Customer Solution Centre Technician
EDS / Hewlett Packard Enterprise
Tallaght
07.2008 - 12.2016
- Supported business-critical banking and payment-processing applications running on HP-UX UNIX within strict SLA-driven production environments.
- Utilized UNIX shell access for operational support, file management, troubleshooting, and controlled production processing; developed Bash scripts to streamline repetitive operational tasks.
- Automated packaging of 200,000+ front-and-back cheque images generated by NCR cheque sorting equipment using UNIX tar utilities, enhancing processing efficiency.
- Collaborated on Informix, SQL, and Perl scripting for enterprise file-transfer and infrastructure monitoring; investigated incidents, resolved error conditions, and coordinated escalations to ensure service continuity.
Clearing Services Support
HP
Sandyford
03.2006 - 06.2008
- Facilitated regulated banking and payment-processing operations, ensuring accurate settlement, reconciliation, and timely reporting.
- Collaborated with clearing operations for Danske Bank and Ulster Bank to streamline manual processes, enhancing operational reliability.
- Ensured smooth execution of daily responsibilities to maintain workflow.
- Contributed innovative ideas and solutions to enhance team performance and outcomes.
- Worked successfully with diverse group of coworkers to accomplish goals and address issues related to our products and services.
Education
Diploma - Networking and Systems Security
City College Dublin
06-2021
Skills
- Microsoft 365 administration
- Azure infrastructure
- Firewall configuration
- Disaster recovery
- Network design
- Virtualization management
- UNIX & Automation: Linux Administration; Bash Scripting; PowerShell; Perl; shell administration; tar; process automation
- Risk management
Personal Information
Title: Senior Systems Engineer | Network Infrastructure | Cybersecurity | Cloud & Enterprise Systems
Affiliations
FME Certified Professional | ITIL Foundation | ISACA Member
Timeline
Senior Systems Engineer
Compass Informatics
10.2023 - Current
Systems Administrator
Compass Informatics
06.2021 - 09.2023
IT Systems Administrator
Lafferty Architects
12.2016 - 05.2021
Customer Solution Centre Technician
EDS / Hewlett Packard Enterprise
07.2008 - 12.2016
Clearing Services Support
HP
03.2006 - 06.2008
Diploma - Networking and Systems Security
City College Dublin