1. What is a Security Engineer at National Grid?

As a Security Engineer at National Grid, you are on the front lines of protecting some of the most critical infrastructure in the world. National Grid operates the systems that deliver electricity and gas to millions of customers across the US and the UK. In this role, your work directly impacts the resilience, safety, and reliability of the energy supply chain, ensuring that both corporate IT networks and critical Operational Technology (OT) environments remain secure against evolving cyber threats.

Your impact extends far beyond standard corporate security. You will be tasked with safeguarding networks that control physical infrastructure, meaning your technical decisions have real-world safety implications. You will collaborate with cross-functional teams, including network operations, compliance, and engineering, to design, implement, and monitor robust security architectures.

This role requires a unique blend of high-level strategic thinking and deep technical execution. Whether you are configuring firewalls, responding to active threats, or aligning systems with strict regulatory frameworks, you are a vital protector of the grid. You can expect a highly structured, compliance-driven environment where precision, accountability, and a calm approach to problem-solving are paramount.

2. Common Interview Questions

3. Getting Ready for Your Interviews

To succeed in the National Grid interview process, you must approach your preparation systematically. Interviewers will look for a balance of deep technical knowledge and the behavioral competencies required to thrive in a highly regulated, safety-first culture.

Focus your preparation on the following key evaluation criteria:

• Technical and Domain Expertise – You must demonstrate a comprehensive understanding of network security, infrastructure protection, and industry-standard security frameworks. Interviewers will evaluate your grasp of core security principles, often probing your knowledge to a depth comparable to professional certifications.
• Situational Judgment and Incident Response – Working in critical infrastructure means you will face high-pressure scenarios. You will be evaluated on how you assess risk, prioritize actions, and respond to potential breaches or system vulnerabilities in real-time.
• Competency and Values Alignment – National Grid places a heavy emphasis on safety, communication, and teamwork. You must show that you can articulate complex security concepts to non-technical stakeholders and collaborate effectively across diverse teams.
• Adaptability and Problem-Solving – You will be tested on your ability to navigate ambiguous technical challenges. Interviewers want to see your structured approach to troubleshooting and how you design secure solutions without disrupting essential services.

4. Interview Process Overview

The interview process for a Security Engineer at National Grid is a multi-stage journey designed to thoroughly assess both your technical capabilities and your cultural fit. The process typically begins with an asynchronous digital assessment. You will face a first-round video interview that includes interactive gaming rounds designed to test cognitive and behavioral traits, followed by pre-recorded video questions where you will introduce yourself and your background.

If you progress, you will move into the preliminary technical screening and in-person or live-virtual interviews. These middle stages are highly variable depending on the hiring manager. Some candidates experience a conversational, calm environment focused on situational and competency-based questions. However, other panels are notoriously rigorous, employing a style that feels akin to an oral exam for a senior security certification. You must be prepared for both extremes.

The final stages involve meeting with broader team members and stakeholders to ensure alignment with the company's operational goals and safety culture. Throughout the process, the emphasis remains on your ability to protect critical systems while maintaining a collaborative, professional demeanor.

This visual timeline outlines the typical progression from the initial digital and gaming assessments through the rigorous technical and behavioral onsite rounds. You should use this to pace your preparation, ensuring your foundational technical knowledge is sharp for the middle rounds while saving energy for the highly situational final interviews. Note that the exact number of technical rounds may vary slightly depending on your specific location and team.

5. Deep Dive into Evaluation Areas

To excel in your interviews, you must understand exactly what the hiring committee is looking for. The evaluation areas below represent the core competencies tested during the National Grid process.

Network and Infrastructure Security

Because National Grid relies heavily on complex, distributed networks, your understanding of network security is paramount. Interviewers will test your ability to design secure network architectures, manage firewalls, and implement robust access controls. Strong performance here means demonstrating both theoretical knowledge and practical application.

Be ready to go over:

• Network Protocols and Routing – Deep understanding of TCP/IP, DNS, BGP, and how to secure them against common attacks.
• Firewall and Perimeter Defense – Configuring, auditing, and managing enterprise-grade firewalls and intrusion detection/prevention systems (IDS/IPS).
• Vulnerability Management – Identifying, assessing, and mitigating vulnerabilities across both traditional IT and specialized OT environments.
• Advanced concepts (less common) – Zero Trust architecture implementation, SCADA/ICS security protocols, and hardware security modules (HSM).

Example questions or scenarios:

• "Walk me through how you would secure a newly deployed segment of our operational network from the corporate IT environment."
• "Explain the difference between stateful and stateless firewalls, and when you would use each."
• "How do you prioritize vulnerability patching when dealing with legacy systems that cannot experience any downtime?"

Situational Judgment and Incident Response

When protecting the energy grid, how you react to a crisis is just as important as your technical skills. Interviewers will present you with hypothetical security incidents to evaluate your composure, methodology, and prioritization skills. A strong candidate will rely on established incident response frameworks (like NIST) rather than guessing.

Be ready to go over:

• Threat Detection and Triage – How you identify false positives versus actual threats in a high-noise environment.
• Containment and Eradication – The steps you take to isolate compromised systems without disrupting critical business operations.
• Post-Incident Review – How you document incidents, communicate with stakeholders, and implement lessons learned.

Example questions or scenarios:

• "You receive an alert indicating unusual outbound traffic from a critical substation network. What are your first three steps?"
• "Describe a time you had to respond to a security incident under extreme time pressure. How did you maintain your composure?"
• "How do you balance the need to contain a malware outbreak with the operational requirement to keep the power grid online?"

Core Competencies and Cultural Fit

National Grid values safety, reliability, and clear communication. The competency-based portion of the interview often feels conversational but is highly structured. Interviewers are looking for evidence of your past behavior to predict your future performance.

Be ready to go over:

• Stakeholder Communication – Translating complex security risks into business terms for leadership and non-technical teams.
• Team Collaboration – Working alongside engineering, compliance, and operations teams to achieve shared security goals.
• Commitment to Safety and Process – Demonstrating a deep respect for strict change-management processes and regulatory compliance.

Example questions or scenarios:

• "Tell me about a time you had to convince a reluctant system administrator to implement a disruptive security patch."
• "Describe a situation where you identified a flaw in an existing security process. How did you go about fixing it?"
• "How do you ensure your daily work aligns with the broader safety and reliability goals of the organization?"