Security Engineer L3

OpenKrill; United States; Remote; USD 110,000 - 180,000; Full time

Job summary

OpenKrill seeks an experienced L3 Security Engineer to lead security engineering, architecture, and continuous improvement across multiple customer environments within an MSP. You will design and implement security controls, lead vulnerability remediation, strengthen compliance, resolve complex incidents, and establish consistent security standards.

You will work closely with infrastructure teams, service desk engineers, Account Managers, and customers, taking ownership of security outcomes

Qualifications

• Experience in an MSP/MSSP or IT service provider.
• Hands-on Defender, Sophos Firewall and endpoint security knowledge.
• Experience managing vulnerabilities and patching across environments.
• Ability to translate compliance requirements into secure controls.
• Strong Windows Server and networking troubleshooting skills.
• Proven lead on remediation activities and incident handling.

Responsibilities

• Lead security engineering, architecture and improvements across customer environments.
• Design and implement security controls and remediation strategies.
• Drive vulnerability remediation and patch programs.
• Establish security standards and ensure consistent enforcement.
• Mentor junior engineers and coordinate with MSP teams and customers.

Skills

MSP/MSSP experience

Defender experience

Zero Trust

Vulnerability management

Patch management

Security architectures

Windows Server troubleshooting

PowerShell scripting

Network fundamentals

Security incident response

Tools

Microsoft Defender

Sophos Firewall

Sophos XDR

Microsoft 365 security

Microsoft Entra ID

ConnectSecure

Huntress

Azure/AWS security tooling

HaloPSA/ConnectWise/Autotask

Job description

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