Undersea Infrastructure
The New Frontline for Cyber and Physical Threats

Although the world’s seas and oceans have long been sites of geopolitical rivalry, a new silent battlefield is forming under the waves. The foundation of our hyperconnected national security and global economy is made up of ports, subsea cables, offshore energy assets and underwater sensor networks. Trillions of daily financial transactions, 99% of worldwide data traffic, and expanding flows of renewable energy from offshore wind farms are carried by these systems. And in recent years, they have emerged as top targets for both cyber disruption and physical sabotage. 

Between 2023 and 2025, a wave of cable cuts and pipeline damage occurred in the Baltic Sea. Similar trends have been seen elsewhere: communication throughout Asia, Europe, the Middle East and Africa was hampered by Red Sea cable cuts in March 2024 and September 2025, while the sabotage of the Nord Stream pipeline in 2022 established a precedent for kinetic hybrid warfare.

These are not one-off incidents. Grey-zone operations utilising covert commercial ships, shadow fleets and unmanned underwater vehicles (UUVs) for seabed reconnaissance and possible sabotage have been connected to state players, especially China and Russia. The Houthis and other non-state actors have shown how even indirect operations, like missile strikes that cause ships to pull anchors, may result in extensive disruptions. The result is economic upheaval, damage to public confidence, and repairs sometimes delayed for months due to a lack of repair ships and security concerns.

Why is subsea infrastructure so alluring and vulnerable? Firstly, underwater infrastructure is challenging to monitor. About 70% of the earth is covered by oceans; pipelines and cables wind thousands of kilometres through disputed or international waters, frequently at depths of more than 1,000 metres. Conventional monitoring is inadequate since patrol boats cannot be everywhere, automatic identification system (AIS) signals can be faked or disabled, and satellite coverage has gaps. Distributed acoustic sensing (DAS) can be used to transform fibre-optic cables and underwater sensors into detection instruments, but legacy systems do not have this capability. Complexities of jurisdiction – where do the high seas start and a coastal state’s power end – make a quick response even more difficult.

Secondly, attackers can easily and cheaply cause disruption. Several cables can be severed by a single pulled anchor, fishing net or UUV. Cyberattacks target offshore platforms’ supervisory control and data acquisition interfaces, landing stations and remote network management systems. The barrier for hybrid actors is lowered by emerging technology such as inexpensive autonomous underwater equipment. Underwater sensors and ports, which are essential for maritime domain awareness, are similarly vulnerable to cyber-physical tampering, mines and diver attacks, likewise the subsea stations and interconnectors of offshore wind farms. 

Thirdly, there is a huge payout potential. A few cuts can isolate islands, impair military communications, stop energy flows or cause economic upheaval without starting a full-scale conflict, giving hostile actors asymmetric leverage. These assets become high-value, low-risk targets for espionage, coercion or destabilisation. A multi-layered approach based on resilience, not only reactivity, is necessary for credible protection. This entails understanding underwater systems as cyber-physical convergences where security must be built in from the beginning.

The cornerstone is resilient design. To prevent choke spots, cables should be buried deeper whenever possible, protected from anchors and trawls, and routed with built-in redundancy and diversity. Segmented, hardened designs are required for offshore energy platforms and interconnectors. Attackers may be discouraged by decoy assets or quick repair options. Traffic rerouting reduces interruptions thanks to network redundancy, which has previously been shown to be effective in Europe’s Baltic responses.

New technology must be used in continuous monitoring. Utilise DAS to transform existing fibre into sensor arrays for real-time vibration and acoustic detection of divers, anchors or UUVs. Track suspicious vessels even when AIS is dark by integrating multi-sensor fusion, which includes radio-frequency detection, electro-optical images, synthetic aperture radar and AI-driven behavioural analytics. Ports and high-value zones can be patrolled by diver-detection sonar, autonomous underwater vehicles and unmanned surface vessels. Predictive analytics, anomaly detection and automatic alerts are areas where AI shines.

It is imperative that stakeholders coordinate more closely: real-time intelligence sharing between telecom carriers, energy firms, maritime authorities and national security organisations, such as Nato’s Critical Undersea Infrastructure Coordination Cell. Public-private collaborations should be expanded to include supply chain vetting, standardised threat-sharing protocols and collaborative exercises. While industry brings innovation, governments can use regulation to encourage resilience. Eighty-five per cent of critical infrastructure is privately owned; success depends on cooperation, trust and shared accountability between operators and regulators.

We must also take precautions against digital contagion in this era of cyber-AI convergence, since a compromised landing station or offshore control system might trigger failures across interconnected industries. Quantum-resistant encryption, constant monitoring and zero-trust concepts are essential. 

Ultimately, protection is more about mission assurance, societal resilience and upholding confidence in the systems that support our day-to-day existence than it is about hardware or software.

The undersea realm is our new front line, not a far-off border. Recent events are not oddities but cautions. We can prevent threats and guarantee the security of these vital lifelines by making investments in robust design, monitoring and public-private coordination. The stakes are high: national sovereignty, energy security and economic stability. Proactive readiness is essential for a safer and more resilient future as we navigate the Fourth Industrial Era.