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The Mediterranean Subsea: Protecting a Super Data Highway

Christian Bueger

University of Copenhagen

The Mediterranean Super Data Highway

The Mediterranean Sea is a super data highway in the global digital economy. On the region’s ocean floor thousands of kilometres of optic fibre cables connect Europe, Africa and Asia. Up to 95% of transregional communications run through these cables.

Digital communications and the internet depend on a physical infrastructure is often forgotten

When we discuss security in the cyber domain, we most often focus on data protection, and threats from hackers and ransomware. The fact that digital communications and the internet depend on a physical infrastructure is often forgotten. It is cables running across the ocean floor that connect islands such as Mallorca, Sicily or Malta to the internet. It is these cables that allow for communication across regions and enable us to send an email to Asia, or access content that is stored on servers abroad. The cyber security and governance debate, however, hardly pays any attention to the resilience of these cables.

The cables lie in the sea, or more accurately on the seabed. So, we could expect debates on maritime security to focus on their protection. Yet, maritime security discussions hardly touches on this area. In the Mediterranean, concerns remain focused on the problems of irregular migration and smuggling.

In this article, I first of all show how and why the Mediterranean is a super highway in contemporary digital communications, and that regional politics must be aware of this. I then proceed in discussing the range of threats that these cables are facing and which measures might be adopted to improve their protection. I end by reflecting how far the incident that occurred in the Baltic Sea in September 2022, the attack on the Nord Stream pipelines, has been a game changer for the debate, and what needs to be taken into account to better protect these cables.

Cable Infrastructure in the Mediterranean

Infrastructure is a key enabler for global flows. Global supply chains depend on roads, railways and ports and energy supplies on a complex European grid. Often such infrastructure, however, resides in the background. It only comes to our minds if it fails. In many ways, infrastructure is designed to be invisible. The same observations can be made with regards to the infrastructure that digital communications and the Internet rely on. Since satellite systems are not reliable enough and cannot handle large amounts of data, it is a complex network of optic fibre cables and landing stations through which contemporary signals flows. These garden hose sized cables connect countries and regions, but since they are infrastructure that are out at sea and on the seabed, they are hardly visible to us. We take their smooth operation for granted.

The Mediterranean is quite a congested space and several vital cables run through the region

The Mediterranean is quite a congested space and several vital cables run through the region. The most important ones are the 16 cables that connect Europe and Asia. These run through the Red Sea and then pass the Maltese coast, from where they connect to France, Italy or go even further through the Strait of Gibraltar all the way up to the United Kingdom. The major landing site for these cables and those that come from Western Africa, is the port of Marseille. In Marseille, 15 cables connect to the terrestrial grid. A multitude of other shorter cables provides connections. This includes international cables, running, for instance, from Italy to Greece, from Morocco and Algeria to Spain or from Libya to Greece. Various cables also connect the Mediterranean islands to the mainland. Indeed, all of the islands are fully dependent on these connections for their internet.

How Vulnerable Is Cable Infrastructure?

There are three kinds of danger to the functioning of the cable network: first, natural disasters; second, accidents that arise from multi-use conflicts; and third, deliberate attacks (Bueger et al. 2022). Out of these the second type frequently occurs and the third is most troublesome.

Natural disasters, such as seaquakes, storms or volcano outbreaks can damage cable systems. These occur less frequently, and are not an immediate concern in the Mediterranean. The most pressing challenges to the network in the region are linked to damage caused by other maritime users. The Mediterranean Sea is a congested maritime space, fishing, marine transport and leisure activities continue to grow. Fishing devices, and ship anchors specifically have the potential to damage cable installations. Indeed, such accidents occur quite frequently and the cable industry attributes, for instance, 30 percent of damages directly to fishing activities (European MSP Platform, 2019).

The third kind of danger is related to deliberate damage. This might be with criminal intent, ranging from theft to causing damage to conceal other criminal operations. Radicals with extremist political motives or state adversaries aiming to disrupt infrastructure could also launch attacks. State adversaries might do so to send political signals through what some refer to as “grey zone tactics” – that is attacks deliberately clouded as accidents or which are difficult to directly attribute to state intent. With ongoing concerns of violent extremism in the region and concerns over Russia’s grey zone operations, it is the latter two scenarios which are most worrying. However, so far, no publicly reported incident meets these criteria

The impact of a single cable failure is typically minimal and goes largely unnoticed by end users. The number of cables implies high levels of redundancy and the cable industry and many countries have re-routing arrangements to ensure digital flows when failures occur. At the same time, repair capacities are limited. The regional cables are serviced through the Mediterranean Cable Maintenance Agreement which is a cooperative with two cable ships based in La Seyne-sur-Mer (France) and Catania (Italy). These ships also service the Red Sea and the Black Sea. This implies that multiple cable failures might have a more severe impact on digital connectivity.

Such risks in particular apply to islands and chokepoints. Since islands are fully dependent on subsea cables, with no terrestrial redundancy, multiple failures can have quite a significant impact. Mallorca, for instance, has four cable connections, three of which come from the Spanish mainland and one from Algeria, while Ibiza depends on a single connection. Sardinia depends on three cables, two from the Italian mainland and one from Sicily, while Malta has five cables to Sicily, and one connecting it to an international cable.

All submarine cables that connect Europe and Asia, with one exception, run through Egypt and the Red Sea

In the Mediterranean there are three major chokepoints – key passage points in which several cables could fail at the same time. With 15 international cables landing in Marseille, the coast is of particular importance. Five important cables run through the Strait of Gibraltar. Most importantly, all submarine cables that connect Europe and Asia, with one exception, run through Egypt and the Red Sea. This is why the coast off Egypt and the Red Sea have been called the “most vulnerable place on the Internet” (Burgess,2022).

How to Protect Underwater Infrastructure

Cable protection involves several layers (Bueger et al., 2022). The first is physical protection through hardening of the cable, burying it in the seabed, and fences and barbwire at their landing stations. This is usually left in the hands of the industry. A second layer is mapping. Cable locations are marked on navigational charts to ensure that other maritime users are aware of their location and avoid fishing and anchoring. Yet, this also implies that it is public knowledge where the cables are laid, meaning they are put at risk of deliberate attacks.

A third layer is surveillance and monitoring. The cables themselves are used by the industry as sensors to detect suspicious behaviour around them and to detect failures. The industry also conducts surveillance of activities on the surface above cable locations. The navies of Mediterranean states, such as France and Italy also have substantial capabilities, known as maritime domain awareness, and are using them to support the surveillance of activities in cable locations. Often, however, maritime security agencies prioritize other issues and threats.

The fourth layer is in the hands of states, and consists of the demarcation of protection and safety zones around cable location in territorial waters and Exclusive Economic Zones as well as enforcing compliance with the respective rules. Finally, cable protection requires transnational cooperation and diplomacy between the states connected by cables. In the northern Mediterranean this is often through the European Union. The importance of cable connections between Europe and North Africa, as well as the chokepoint in Egypt, however, have not featured high on that agenda. 

Protection after the 2022 Nord Stream Attack

The European Union, NATO and its Member States have given heightened attention to the protection of cables since September 2022. When in the Baltic Sea several explosions damaged the Nord Stream pipelines, it brought the vulnerability of underwater infrastructure to wider public attention. As a major wake-up call, the event also documented how difficult it is to do effective surveillance, or even prosecute perpetrators (Bueger, 2022). The identity and methods of the perpetrator(s) responsible for the sabotage remains unknown eight months after the events.

Both the European Union and NATO have launched a range of instruments to improve the protection of critical maritime infrastructure

Both the European Union and NATO have launched a range of instruments to improve the protection of critical maritime infrastructure. Under this agenda, attention is given to the full range of critical maritime infrastructure, including those on the ocean floor. In addition to data cables, the focus is on oil and gas platforms and pipelines, as well as wind farms and the underwater electricity cables that connect them to the land. This lens is important given the similar threat landscape for all these kinds of infrastructure.

The two organizations aim at improving risk analyses, maritime and underwater domain awareness through autonomous systems, as well as enhancing cooperation with the industry. These are promising new directions. Much of the attention, however, has been so far been directed towards the Baltic Sea, North Sea and Atlantic. The substantial vulnerabilities in the Mediterranean, by contrast, are not well understood. Appropriate solutions need to be found, which require close cooperation with the North African coastal states and their industries, as well as investments in capacity-building for enhanced protection.


Bueger, Christian and Liebetrau, Tobias. “Governing hidden infrastructure: The security politics of the global submarine data cable network.” Contemporary Security Policy 42(3): 391-413, 2021.

Bueger, Christian; Franken, Jonas and Liebetrau, Tobias. “Security threats to undersea communications cables and infrastructure – consequences for the EU.” In-Depth Analysis for the European Parliament commissioned by the Sub-Committee on Security and Defense, 1 June 2022,

Bueger, Christian. “Can Europe protect its underwater cables from sabotage?” EU Observer, 11 October 2022,

Burgess, Matt. “The most vulnerable place on the internet.” Wired Magazine, 2 November 2022,

European MSP Platform. “Conflict fiche 2: Cables/Pipelines and commercial fisheries/ shipping.”, 2019.

(Header photo: A single-mode fibre optical cable with light passing through | chaitawat, CC0, via Wikimedia Commons)