Strengthening the security and resilience of Europe’s submarine cables 

Submarine cables carry approximately 97–98% of global internet traffic, and despite its extensive terrestrial networks, the EU is no less dependent on these infrastructures than other regions of the world.  In response to these challenges, the European Commission and the High Representative of the Union for Foreign Affairs and Security Policy adopted the EU Action Plan on Cable Security on 21 February 2025.  

Action plan

The Action Plan sets out coordinated measures to enhance the security and resilience of submarine telecommunications and power cables, covering the full resilience cycle: prevention, detection, response and recovery, and deterrence. It builds on earlier initiatives, notably Commission Recommendation (EU) 2024/779 on Secure and Resilient Submarine Cable Infrastructures, as well as the NIS2 Directive and the Directive on the resilience of critical entities (CER)  

To support the implementation of Recommendation (EU) 2024/779, the Commission established the Submarine Cable Infrastructures Expert Group, bringing together Member State authorities and ENISA (European Union Agency for Cybersecurity).  One of the Group’s key deliverables is a comprehensive report on the mapping of existing and planned submarine cable infrastructures, a Union-wide risk assessment, and stress test guidance for cable security and resilience  

Submarine cable infrastructure  

The report highlights significant structural trends in the submarine cable market. Over the past decade, the share of cable capacity owned by traditional European telecom operators has declined sharply, while US hyperscalers now dominate major intercontinental routes, owning around 90% of capacity on the transatlantic route. In 2024, hyperscalers accounted for 71% of all used international capacity, compared with just 10% in 2014. As a result, EU Member States are becoming increasingly reliant on non-EU actors for connectivity to North America and potentially to Asia and Africa, raising concerns about technological sovereignty and economic security  

The mapping exercise also shows that submarine cable capacity connecting the EU grew from 318 Tbit/s in 2010 to 3 755 Tbit/s in 2024. However, this capacity is unevenly distributed across cable generations. While the 33 newest cables provide 74% of total capacity, the oldest 89 cables account for only 2%, yet they still carry a significant share of public telecom traffic. As these legacy cables reach end-of-life, operators will need to secure capacity on newer systems to ensure continuity of services. 

Resilience and maintenance 

On resilience and maintenance, the report finds that the number of submarine cable faults in Europe has declined, particularly in Northern Europe, due to improved cable design, better laying standards, education in the fishing community, and the decommissioning of vulnerable legacy cables. Between 2022 and 2024, only 2–3% of incidents involved delays in vessel mobilisation beyond 24 hours, suggesting that the current repair fleet is adequate under business-as-usual conditions. However, the report warns that this situation could change rapidly if maintenance vessels are withdrawn, repurposed, or damaged, or if capacity is increasingly absorbed by hyperscaler-led deployments  

Detection and monitoring  

These are a central pillar of the EU Action Plan on Cable Security. The documents recognise that the EU currently lacks an integrated capability to monitor threats to submarine cable infrastructures in real time. To address this gap, the Action Plan calls for the development of voluntary integrated surveillance mechanisms per sea basin, the exploration of networks of submarine sensors, and the use of air, surface and underwater surveillance technologies. It also highlights the potential of SMART cables, which integrate sensor and monitoring functions directly into cable systems, to support early detection of threats and incidents. These measures aim to improve situational awareness, enable faster identification of disruptions, and reduce response times in the event of damage to critical submarine cable infrastructure.  

Electronic detection systems 

Examples of electronic detection systems include optical fault-location technologies such as Optical Time Domain Reflectometry (OTDR), which allow operators to detect and precisely locate breaks or faults along fibre-optic submarine cables. In addition, distributed fibre-optic sensing systems, such as Distributed Acoustic Sensing (DAS), can detect vibrations, strain or disturbances along a cable, helping to identify potential damage from anchors, fishing activity or seabed movement. 

Overall, the Expert Group’s work provides a critical evidence base for EU policy action. By combining detailed infrastructure mapping, a consolidated risk assessment, and stress test guidance, it supports the implementation of the EU Action Plan on Cable Security and underlines the strategic importance of submarine cables for Europe’s digital resilience, economic security and strategic autonomy.