NB8 Series. Protecting Critical Undersea Infrastructure: Enhancing NB8 Maritime Security Cooperation

Critical undersea infrastructure encompassing various energy and data connections underpins economic cooperation among the Nordic-Baltic Eight (NB8).

But a turbulent geopolitical environment has exposed its vulnerabilities. To reduce risks, the NB8 need to enhance security cooperation, innovation, and defence-industrial coordination.

Risks

The EU and NATO responded to Russia’s full-scale aggression in Ukraine by strongly supporting Kyiv. Western government officials and media commentators have accused Russia of retaliating in turn with a ‘shadow war’ against the West, possibly in collusion with other state and non-state actors. For example, Russia retains close strategic cooperation with Belarus, while China discreetly supports Russia’s war.

A US Helsinki Commission report confirmed or suspected 150 instances of Russian hybrid operations against NATO member states in 2022-2024. Russian intelligence agencies are also reported to be running a ‘gig economy’ for hybrid activity and outsourcing sabotage and espionage assignments to illicit actors. This has fostered suspicion that recent incidents affecting undersea infrastructure in the Baltic Sea have been the result of sabotage.

In October 2023, the Hong Kong-registered vessel NewNew Polar Bear damaged the Balticconnector gas pipeline between Estonia and Finland, taking it out of service for six months. Multiple data cables were also ruptured. Interference from the Chinese-flagged Yi Peng 3 was suspected when the undersea BCS East-West Interlink data cable between Lithuania and Sweden and the C-Lion1 data cable between Finland and Germany were damaged in November 2024. Finnish prosecutors charged crew from the Cook Islands-flagged oil tanker the Eagle S with criminal offences relating to a December 2024 incident in which the undersea Estlink 2 electricity connection and four data cables were damaged. However, the case was later dismissed by a Helsinki court as the reported damage occurred outside Finland’s territorial waters.

Whether these episodes can be directly tied to Russian interference or, as some sources suggest, are a result of negligence, poor seamanship and inadequate levels of maintenance in Russia’s ‘shadow fleet’, these disruptions present a significant challenge in proving intent. NATO enhanced its military presence in the Baltic Sea in January 2025 with the launch of a new military activity, ‘Baltic Sentry’, intended to strengthen the protection of critical infrastructure.

Meanwhile, the NB8’s push to diversify energy supplies creates fresh concerns about the possibility of increased hybrid disruption in the maritime domain. NB8 governments are currently exploring options that would limit over-dependence on undersea connections. For example, Estonia plans to phase out oil shale electricity production by 2040 to meet EU environmental targets and is considering bridging supply gaps with domestic nuclear power plants, smaller gas facilities, and renewables. At the same time, the rapid expansion of offshore wind capacity in the region will add more subsea (and surface) infrastructure, while major projects such as Estlink 3 will provide greater redundancy in transmission capacity, but also introduce new vulnerabilities on the Baltic seabed.

Undersea connections will thus remain important for regional energy security. Safeguarding this infrastructure is essential to underpin national economies, resilience and NB8 integration. Preventing interference will require stronger legal and political cooperation, but also practical cooperation in the security sphere.

Evolving cooperation

As the NB8 format lacks the structures and capacity for governance, its members should respond to this challenge primarily by coordinating their approaches within multiple cooperation formats. NATO is the main organisation within which the NB8 can pursue defence cooperation with other states having critical strategic interests in the wider Baltic Sea, such as the US, Canada, Poland and Germany. It is also the key organisation through which military interoperability at all levels is generated. At the same time, regional defence formats like the Joint Expeditionary Force (JEF) and Nordic Defence Cooperation (NORDEFCO) can help tailor solutions to local conditions and security needs.

The NB8 can also coordinate with the EU, whose developing role includes the establishment of regulatory and financial measures that seek to deter, detect, and respond to subsea cable incidents. Clearly, there is a potential here for overlap or duplication with NATO, underlining the importance that NB8 countries should attach to promoting effective EU-NATO cooperation.

A particular priority for maritime security in the Nordic-Baltic region is building better Maritime Domain Awareness (MDA) defined by the International Maritime Organization as effective policy understanding of maritime security, safety and economics. This is essential for securing critical undersea infrastructure and, necessarily, a cooperative venture. But it remains underdeveloped in the region, particularly when it comes to monitoring commercial vessels operating near undersea infrastructure.

Closer NB8 coordination inside NATO’s Critical Undersea Infrastructure Coordination Cell, for example, would provide opportunities to strengthen public-private cooperation, policy development and implementation to bolster NATO and regional MDA. Established in February 2023, the cell maps vulnerabilities, and coordinates efforts between NATO allies, partners, and the private sector as well as contributing to NATO’s Digital Ocean Initiative. Coordination on aspects of NATO’s space policy, meanwhile, will be necessary to ensure that space-based surveillance assets can also contribute to maintaining the maritime picture of the Baltic Sea.

MDA also depends on successful inter-agency cooperation. The NB8 can share best national practices in this area to ensure opportunities for international cooperation between non-military agencies including police, customs, border guards, intelligence services and commercial operators of energy and data infrastructure.

Leading on technology

One area in which the NB8 might seek a higher profile as a distinct regional entity is in the cooperative development and promulgation of advanced defence technologies for MDA and broader maritime security solutions. NB8 countries already have strengths in these fields to build upon. Finland, for example, has hosted NATO trials integrating Uncrewed Maritime Systems, Uncrewed Surface Vessels with advanced sensors, Autonomous Underwater Vehicles, and Tethered Uncrewed Aerial Systems with continuous power and data connectivity. NATO Allied Command Transformation’s Task Force X, which operates alongside ‘Baltic Sentry’, is exploring the use of autonomous and AI systems in maritime operations.

EU instruments such as the European Defence Fund (EDF) also provide opportunities to further strengthen the NB8’s innovation base. Norwegian and Swedish companies, for example, participate in the EDF’s E-DOMINION project for digitalising naval platforms and developing integrated combat cloud capabilities for maritime operations. Meanwhile, the Estonian company, Baltic Workboats, leads the EDF’s EUROGUARD project to research and develop a modular and semi-autonomous surface vessel prototype.

Finally, the NB8 countries can build on their close relations with Ukraine to facilitate the transfer of the innovative tactical, operational, and strategic concepts, along with the technology and defence-industrial knowledge that Kyiv has developed since 2022. Alongside lobbying for greater Ukrainian participation in NATO and JEF exercises, NB8-Ukraine cooperation can support the sharing and further development of operational and policy responses and technology to ensure that lessons from the conflict are promulgated across NATO’s maritime domain.

Policy Recommendations

• The NB8 should prioritise a regional maritime security approach that seeks to maximise coordination and cooperation within existing multilateral formats, in particular NATO and the EU.
• NB8 countries should also use the JEF and NORDEFCO to better tailor maritime security solutions to local needs and to involve other partners that contribute to security in northern Europe.
• NB8 countries should, as a priority, strengthen MDA for maritime operations in northern Europe by enhancing surveillance capabilities, and by facilitating secure information exchanges between military forces, government agencies and commercial infrastructure operators, nationally and internationally.
• Governments and private industries within the NB8 should aim to improve NATO’s MDA through active engagement in NATO’s Undersea Infrastructure Coordination Cell.
• NB8 countries should seek a leading role, as a regional entity, in the development of advanced maritime technology, by leveraging local innovation and enhancing joint procurement initiatives to address emerging hybrid threats and strengthen collective resilience.
• NB8 governments should introduce measures for encouraging the region’s defence industries and driving the NB8’s defence innovation-base, including measures to facilitate their participation in the EDF and ReArm Europe more broadly.
• They should build on the region’s close relationship with Ukraine to ensure that doctrinal, technological, and defence-industrial lessons are disseminated across NATO’s maritime domain.

Eoin Micheál McNamara acknowledges research funding through the Reignite Multilateralism via Technology (REMIT) project, funded from the European Union’s Horizon Europe research and innovation programme under grant agreement No. 101094228.

Read also:

• Brief 1. How to Implement a Full Maritime Services Ban on Russian Oil (Henrik Wachtmeister, Daniel Spiro, Henrik Praks)
• Brief 2. The Circles of Security: The Role of the NB8 in (Northern) European Security (Hiski Haukkala, Kristi Raik)
• Brief 3. Geo-economic Resilience: Collective Measures Against the Weaponisation of External Dependencies in the NB8 Region (Thorsteinn Kristinsson, Ludvig Broomé)

About the NB8 Policy Brief Series

The NB8 series of jointly published topical briefs is a collaboration between eight leading institutes in the Nordic–Baltic region. Its purpose is to deepen understanding of the evolving security, political, and societal dynamics shaping the Nordic–Baltic region in an era of renewed great-power competition. The series aims to generate shared insight, foster informed policy dialogue, and contribute to the region’s strategic resilience. The views expressed in the policy briefs are those of the author(s) and do not necessarily reflect the positions of the participating institutes.

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