The UK’s energy sector—spanning power generation, utilities, renewables, oil and gas—has become a prime target for cyber-attacks. As operators of Critical National Infrastructure (CNI), these organisations face constant threats from cyber criminals, state-sponsored groups, and hacktivists. Yet, many still rely on reactive security postures, outdated defences, and minimal testing.

In today’s threat landscape, offensive cyber security strategies—especially CHECK penetration testing with Aristi—are essential tools for identifying vulnerabilities before attackers do. Offensive security isn’t about waiting for an incident. It’s about simulating one under controlled conditions to expose weak points, assess risk, and improve defences.

Why Offensive Security Matters for the Energy Sector

Energy organisations operate complex environments that combine traditional IT systems with legacy operational technology (OT). This convergence introduces new attack surfaces—and traditional security audits simply aren’t enough.  At Aristi, we have vast experience in large capital, national infrastructure projects as we become a cyber security partner that can provide reassurance on systems before go-live, and during the lifecycle of the system: prevention of vulnerabilities in a pre-prod and indeed live environment is better than cure.

Offensive security enables organisations to answer crucial questions:

• What would an attacker do with access to our systems?
• How quickly can we detect, contain, and respond?
• Where are the gaps—in people, processes, or technology?

By identifying and exploiting vulnerabilities before malicious actors do, offensive security helps energy firms become proactive, not reactive.

What Is CHECK Penetration Testing?

The CHECK scheme, developed by the UK’s National Cyber Security Centre (NCSC), certifies providers to deliver government-grade penetration testing. At Aristi, we have over 20 CHECK-accredited testers that can simulate real-world attacks on networks, systems, and applications to identify exploitable vulnerabilities.

For the Energy sector and in particular CNI, CHECK penetration testing ensures:

• Rigorous and trusted assessments that meet government and regulatory expectations.
• Testing aligned with NCSC guidance, including the Cyber Assessment Framework (CAF).
• Key Offensive Security Threats in Energy Environments
• Network Segmentation Failures: Penetration testers often find inadequate separation between corporate IT and critical OT systems, allowing lateral movement by attackers.
• Credential Harvesting & Privilege Escalation: Weak access controls, reused passwords, and poorly protected admin credentials can be exploited quickly.
• Unpatched Systems and Legacy Tech: Many OT environments rely on ageing hardware and software with known vulnerabilities—ripe for exploitation during testing.
• Misconfigured Cloud & Supervisory Control and Data Acquisition (SCADA) Interfaces: Cloud-connected energy management systems and poorly secured web interfaces present a major attack vector.

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The Unique Challenges of Testing Air-Gapped & Offline CNI Systems

Many energy sector environments include air-gapped, isolated, or offline systems that control critical infrastructure. While these networks are physically or logically separated from the internet, they are not immune to attack—especially from insider threats, supply chain compromises, or malware introduced via removable media.

However, testing these systems poses significant challenges:

• Safety and Availability Risks: Unlike IT networks, OT systems control real-world processes (e.g., turbines, substations, pipelines). Penetration tests must be carefully scoped to avoid triggering system failures or downtime. This is where Aristi’s consultants’ experience comes in as we have tested these often unique and custom designed OT systems for many, many projects.
• Access Restrictions: Air-gapped systems often have no remote access, requiring on-site presence and physical security clearance—making testing logistically complex.
• Testing Constraints: Tools and techniques used in conventional Red Team exercises may not be safe or compatible with legacy OT devices, requiring specialised tools and skills.  Our consultants are trained to consider basic security principles and then apply them to the technology they face to test its security posture at a fundamental and complex level.  “What could an attacker do?” is the thought-process.
• Regulatory and Operational Oversight: Any offensive security exercise must be tightly coordinated with operations teams, regulators, and compliance officers to ensure system integrity.

Despite these hurdles, offensive security in air-gapped environments is essential. Controlled simulation of attack paths—combined with passive assessments and physical security reviews—can help identify exploitable weaknesses before they are used against critical systems.

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Physical Security Assessments

While cyber threats often dominate the conversation, physical security and human behaviour are just as critical. A determined attacker may not need to hack into a system—they may simply walk in.

Key Scenarios in Physical Assessments for Energy Environments:

• Tailgating and Access Bypass: Gaining physical access to substations, data centres, or control rooms through social engineering or poor access controls.
• Badge Cloning or Access Token Theft: Cloning RFID badges or harvesting authentication devices left unattended by staff.
• Device Seeding: Planting malicious USB devices in office areas or control rooms to compromise connected systems.
• Pretexting and Impersonation: Red Team operators may pose as contractors, inspectors, or delivery personnel to access restricted areas or coax credentials from staff.
• Dumpster Diving: Retrieving discarded documents, passwords, or internal procedures from improperly disposed materials.

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Why It Matters

Physical and human-layer attacks are often low-tech but highly effective. They reveal blind spots in access control, staff training, and surveillance coverage—critical weak points in an otherwise well-secured operation.

Red Team assessments that include physical intrusion testing and social engineering simulations provide a wholistic understanding of how attackers might gain an initial foothold in CNI environments. Aristi provide these physical assessments in many of our CNI engagements, in particular.

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How Aristi Supports the UK Energy Sector

In conclusion, at Aristi we are a CHECK-approved provider and trusted cyber security partner to CNI and energy organisations across the UK. Our offensive security services are designed to uncover vulnerabilities, test defences, and build resilience in high-risk environments—including complex air-gapped systems.

Our offensive cybersecurity services include:

• CHECK Penetration Testing – Certified testing for IT, OT, and hybrid environments
• Red Team Operations – Realistic adversary simulations targeting high-value assets and offline systems
• Phishing Campaigns & Social Engineering – Testing human vulnerabilities across your workforce
• Incident Response Testing – Assessing your readiness under pressure through tabletop exercises
• Purple Team Engagements – Improving coordination between blue and red teams

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Ready to Test Your Real-World Defences?

Whether your environment is connected, air-gapped, or hybrid, offensive security is the most effective way to build true cyber resilience. With threats becoming more sophisticated and persistent, simulated attacks are no longer optional—they’re mission-critical.

Get in touch with us via the Contact form below to learn how CHECK penetration testing and advanced Red Teaming can help secure your operations, meet compliance, and protect the UK’s Energy infrastructure.

Michael Palmer, Sales Director

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