About the Role We are seeking an experienced L3 Security Engineer to lead security engineering, architecture, and continuous improvement across multiple customer environments within a Managed Service Provider (MSP). This senior technical role goes beyond security monitoring and alert triage. You will design and implement security controls, lead vulnerability remediation, strengthen compliance, resolve complex security incidents, and establish consistent security standards across customer environments. Working closely with infrastructure teams, service desk engineers, Account Managers, and customers, you will take ownership of security outcomes while mentoring junior engineers and driving a proactive approach to cybersecurity. About the Client You will be working with a technology and managed services provider supporting multiple customer environments. The organisation is focused on strengthening cybersecurity, improving service delivery, and developing scalable security standards that help customers reduce risk and maintain resilient IT environments. Ideal Profile Technical Expertise • Significant experience within an MSP, MSSP, or IT Service Provider environment • Strong hands-on experience with Microsoft Defender and its security ecosystem • Advanced experience with Sophos Firewall and endpoint security technologies • Proven experience managing vulnerability and patch management programs • Experience implementing security controls across Microsoft 365 environments • Strong knowledge of Microsoft Entra ID and Zero Trust security principles • Solid understanding of networking fundamentals, including TCP/IP, DNS, DHCP, VLANs, routing, firewalls, VPNs, and network segmentation • Strong Windows Server and endpoint troubleshooting capabilities • Experience handling complex technical escalations and leading remediation activities • Ability to design and implement practical security improvements rather than simply identify risks Security Platforms & Technologies • Hands-on experience with ConnectSecure and Huntress is highly desirable • Experience with Sophos ZTNA, Microsoft Intune, Microsoft Defender XDR, and Conditional Access is advantageous • Familiarity with Microsoft Defender for Endpoint, Office 365, Identity, and Vulnerability Management • Knowledge of Essential Eight, CIS Controls, NIST Cybersecurity Framework, and ISO 27001 • PowerShell scripting and API-based automation experience is beneficial • Familiarity with MSP PSA platforms such as HaloPSA, ConnectWise, or Autotask • Relevant Microsoft, Sophos, or cybersecurity certifications are advantageous Security Architecture & Compliance • Experience assessing security architectures and identifying technical weaknesses • Ability to translate compliance requirements into practical security controls • Strong understanding of cybersecurity threats, attack techniques, and defensive measures • Experience developing remediation strategies, security baselines, and technical standards • Ability to prioritise vulnerabilities based on exploitability, exposure, asset criticality, and business impact Leadership & Communication • Strong written and verbal English communication skills • Excellent technical documentation and reporting capabilities • Ability to lead complex remediation activities and provide technical direction • Confidence making technical decisions and challenging inadequate security practices • Strong problem-solving skills and a methodical approach to incident investigation • Ability to remain calm during critical incidents while considering customer priorities and operational impact • A proactive mindset focused on root causes, automation, standardisation, and preventing recurring issues Responsibilities Security Architecture & Technical Leadership • Act as a senior technical authority for security across multiple customer environments • Design, review, and improve customer security architectures • Establish security standards, recommended configurations, and repeatable best practices • Identify architectural weaknesses and develop remediation roadmaps for complex or high-risk issues • Review security solution designs and support customer onboarding, migrations, and major infrastructure changes • Mentor L1 and L2 engineers and strengthen internal security capabilities • Lead complex security escalations and configuration investigations Microsoft Defender • Administer, configure, and optimise Microsoft Defender security solutions across customer environments • Design and implement Defender policies and standard configurations • Configure and maintain Attack Surface Reduction rules, endpoint detection and response, automated investigation, web filtering, endpoint firewall policies, device control, antivirus, and tamper protection • Investigate complex security incidents involving endpoints, identities, email, and cloud environments • Use Microsoft Defender XDR to conduct advanced threat analysis • Review Secure Score, vulnerability data, and security exposure to identify improvement opportunities • Support migrations from third-party endpoint security platforms where appropriate • Identify opportunities to improve Microsoft licensing utilisation and security capabilities Sophos Firewall & Endpoint Security • Provide senior technical support and architecture guidance across Sophos security environments • Design and review firewall deployments and establish standard configuration baselines • Configure and optimise firewall rules, network segmentation, NAT, intrusion prevention, web filtering, application control, VPNs, SD-WAN, high availability, logging, and monitoring • Troubleshoot complex firewall, connectivity, and endpoint security issues • Review configurations for security weaknesses and unnecessary exposure • Manage Sophos Central and endpoint security policies • Support firmware upgrades, migrations, firewall refreshes, and security platform consolidation Zero Trust Network Access • Design, implement, and maintain Zero Trust