Learn what critical national infrastructure is, the threats it faces, and how organizations protect essential services and maintain resilience.
Critical national infrastructure covers power grids, water systems, healthcare, financial networks, communications, transport, and other infrastructure where disruption can have serious consequences for the nation.
Protecting these systems means knowing what infrastructure is critical, how different sectors depend on each other, and which threats could interrupt essential services. It also means having a plan for keeping operations running when an attack, outage, or supplier failure affects systems that teams normally rely on.
This guide covers what critical national infrastructure means, the sectors that make up CNI in the UK and the US, the threats they face, and the measures organizations use to protect them. We also look at an important part of operational resilience: how teams can continue coordinating a response when their usual communication systems are unavailable or compromised.
To see how Wire keeps CNI teams connected during a crisis, book a demo with our team.
Key takeaways
Critical National Infrastructure (CNI) is the set of assets, systems, and networks a country depends on to function. It spans across energy, water, transport, communications, healthcare, finance, defense, and government services. The UK's National Protective Security Authority (NPSA) defines CNI as those elements of national infrastructure whose loss or compromise could cause major harm to essential services, significant loss of life, or serious damage to national security and the economy.
CNI includes both physical and digital assets. For example, a power substation, a water treatment plant, and a hospital building are physical infrastructure. The industrial control systems that run them, the networks that connect them, and the software that monitors them are digital infrastructure, and modern CNI depends on both working together.
In the UK, the NPSA also emphasizes the connected nature of essential services where a failure in one area can affect other sectors that depend on it, increasing the possibility of cascading consequences.
Critical national infrastructure matters because it includes foundational physical and digital systems a country depends on, like electricity generation, drinking water, mobile networks, hospitals, payment systems, and transport services.
Due to the connected nature of different sectors of CNI, disruption in any one of these essential categories can have cascading effects across a country. For example, a major electricity outage could affect telecommunications infrastructure, transport systems, healthcare facilities and emergency services at the same time. The affected organizations then have their own dependencies, which can amplify the original disruption.
That interdependency is why CNI protection has to cover resilience and recovery alongside prevention. CNI security teams can’t assume that every attack will be stopped. So they should plan for what happens when systems become unavailable or untrusted.
CNI operators face a wide range of risks, including cyberattacks, physical disruption, environmental events, and human error. As systems become more connected and reliant on third-party providers, threats can enter through parts of the environment that operators don’t directly control.
Threat actors target critical infrastructure cybersecurity through control-system intrusions, data exfiltration, and denial-of-service attacks designed to disrupt operations rather than just steal information. Ransomware groups have specifically targeted CNI operators because the pressure to restore services quickly makes them more likely to pay.
Unauthorized access, deliberate equipment damage, theft, and sabotage can affect physical facilities and systems like substations, pipelines, water facilities, and transport hubs. Organizations therefore need physical protection as part of critical infrastructure security, including controlled access to sensitive sites and systems, monitoring, appropriate perimeter controls, and procedures for responding to physical incidents.
State-sponsored groups conduct long-term, well-resourced campaigns against CNI to gather intelligence, establish persistent access, or prepare for future disruption. For example, an attacker who compromises an employee account or device could gain access to an internal communication platform, monitor sensitive conversations, and remain undetected while collecting information about systems, personnel, or incident procedures. They could then use that access during a crisis to obtain operational intelligence or interfere with coordination.
Hurricanes, floods, wildfires, and extreme heat events increasingly disrupt CNI operations, and the frequency of severe weather events has made this category harder to plan around using historical data alone. Physical damage to facilities often triggers cascading failures in dependent sectors.
Malicious insiders may intentionally expose information or disrupt systems, while employees and contractors can unintentionally cause incidents through compromised credentials, misconfiguration, unsafe information sharing, or human error.
Here are some best practices for secure internal communication to reduce the risk of insider threats.
Reliance on suppliers, cloud providers, and managed service providers has significantly expanded the CNI attack surface. The UK's Cyber Security and Resilience Bill formally recognizes this as concentration risk, bringing managed service providers and data centers into regulatory scope because a single compromised supplier can now affect the security of thousands of downstream organizations at once.
Protecting critical infrastructure systems requires a combination of cyber resilience, physical security, operational resilience, and incident preparedness. These layers work together to reduce risk and ensure continuity of essential services. The exact controls will depend on the sector, assets, and threats involved, but here are some principles that apply across CNI environments.
Organizations first need to understand what they are protecting and what would happen if it became unavailable.
That process should identify:
This mapping helps security leaders prioritize resources according to impact rather than applying the same controls to every asset.
Protecting CNI physical assets requires controls around facilities, equipment, and sensitive operating areas, especially at power plants, water treatment sites, and nuclear installations where physical compromise can have safety consequences.
Some ways it can be done include limiting access according to operational need, with processes for granting, reviewing, and revoking permissions.
Operational technology and industrial control systems require their own security approach, distinct from standard IT controls. Network segmentation, least-privilege access, patching where operationally feasible, continuous monitoring, and reducing unnecessary connectivity between high-risk systems all help limit how far an intrusion can spread once it gains a foothold.
CNI security teams need to detect suspicious activity early enough to contain it before it disrupts critical operations. They should continuously monitor networks and endpoints, address vulnerabilities, restrict privileged access, and investigate unusual behavior that could indicate a compromised account or system.
Teams also need to secure the information employees exchange during daily operations and incident response. They should protect sensitive operational plans, incident details, and credentials with enterprise cybersecurity solutions that prevent unauthorized access.
The 72 hours after a cyber incident are critical in ensuring the attackers don’t gain access to sensitive information. Here’s a 72-hour crisis response plan for cyber incidents to help you act fast and stay compliant with GDPR/NIS2.
A CNI operator's ability to recover quickly depends on how well they can plan before an incident occurs. A critical infrastructure continuity plan should include:
For a deeper look at building this out, see our guides on incident response planning and business continuity.
Incident response in a CNI environment depends on trusted coordination between security teams, executives, frontline employees, suppliers, government bodies, and emergency responders, often across organizational boundaries. Before an incident happens, it's worth asking a few direct questions about your enterprise communication solution.
Critical infrastructure sectors in the US and the UK include communications. That’s why choosing a secure collaboration tool that prevents security breaches like cyberattacks and provides frameworks to contain incidents once they occur is important. Let’s understand this in more detail below.
Communications is formally recognized as a CNI sector in both the UK and US. In practice, that sector's official scope centers on telecom networks, internet service providers, satellite infrastructure, and the physical and network layer that carries communication traffic across the country. Critical infrastructure security solutions rarely extend to the messaging, calling, and collaboration software that CNI staff, security teams, and cross-agency partners use day-to-day.
That distinction creates a real gap where communication tools are almost always evaluated as productivity tools rather than critical infrastructure resilience infrastructure, which leads to:
Here’s how Wire acts as a secure messenger for companies in multiple sectors.
Wire provides a secure communication and collaboration layer that can support critical infrastructure security solutions alongside an organization's OT security, network security, threat-detection, and incident-response systems.
CNI organizations may have strict requirements for where their communication infrastructure runs and who controls it. Wire's government offering is built around always-on E2EE, private cloud and on-premises deployment options, secure federation between independently administered environments, and enterprise identity and device controls, all designed for organizations that can't accept the sovereignty trade-offs common in mainstream collaboration platforms.
CNI sectors must coordinate with other sectors or external companies to maintain operations. For example, energy providers depend on telecoms, transport systems rely on power and signaling vendors, and healthcare organizations coordinate continuously with suppliers, regulators, and emergency responders.
Wire enables teams to communicate securely with external organizations through E2EE messaging, calls, video conferencing, and file sharing. Organizations can bring external partners into controlled conversations using guest and external access, while maintaining governance over how those participants interact with internal teams. This gives incident responders, suppliers, and partner agencies a secure way to exchange information without moving coordination to unmanaged consumer channels.
Wire Bund, Wire's dedicated government variant, has received VS-NfD approval from Germany's Federal Office for Information Security (BSI), the German government classification equivalent to NATO Confidential. For CNI audiences, it shows that Wire has already built a product to the standard required for highly sensitive government communication, which matters when evaluating whether a communication platform can meet your sector's classification requirements.
When your primary collaboration environment is involved in an incident, response teams still need to communicate while investigation and recovery continue.
Wire can operate as an independent secure communication layer and supports capabilities relevant to this scenario:
More than 1,800 organizations, including government agencies and mission-critical operators, already rely on Wire for exactly this kind of resilient, sovereign communication infrastructure. If your organization operates within critical national infrastructure, book a demo to see how Wire fits into your existing resilience strategy as a secure communication tool.
Critical infrastructure protection (CIP) is the practice of securing the assets, systems, and networks essential to national security, public safety, and economic stability. It combines physical security, cybersecurity, risk assessment, and resilience planning to reduce the likelihood of disruption and limit the impact when disruption does occur.
Under CISA's PPD-21 framework, the 16 US critical infrastructure sectors are Chemical, Commercial Facilities, Communications, Critical Manufacturing, Dams, Defense Industrial Base, Emergency Services, Energy, Financial Services, Food and Agriculture, Government Facilities, Healthcare and Public Health, Information Technology, Nuclear Reactors, Materials, and Waste, Transportation Systems, and Water and Wastewater Systems.
In a cybersecurity context, critical infrastructure refers to the digital systems, networks, and control technologies that operate physical CNI assets, including industrial control systems, SCADA networks, and the IT infrastructure that monitors and manages them.
Responsibility is shared between government bodies and private operators. In the UK, NPSA and the NCSC provide protective security and cyber guidance to CNI operators. In the US, CISA coordinates protection across sectors alongside designated Sector Risk Management Agencies. Individual operators remain responsible for implementing controls within their own organizations.
CNI operators are typically subject to sector-specific regulation alongside broader cyber resilience frameworks, including the UK's Network and Information Systems Regulations and Cyber Assessment Framework, the EU's NIS2 Directive, and, for financial services, DORA. In the US, PPD-21 sets the overarching policy, with individual sector regulators adding further requirements on top of it.
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