Undersea Cable Security Threat — Critical Infrastructure Risk Assessment 2026

STRATEGIC OVERVIEW

Undersea fiber-optic cables form the invisible backbone of the global digital economy, carrying over 95% of international data traffic. These cables connect continents and underpin internet connectivity, financial transactions, military communications, and global trade systems. Without them, the modern interconnected world would cease to function.

As of 2026, rising geopolitical tensions and the mainstreaming of hybrid warfare strategies have brought renewed and urgent attention to the vulnerability of these networks. Recent incidents in the Baltic Sea, North Atlantic, and other strategically sensitive regions have intensified concerns about potential deliberate sabotage or covert interference by state actors seeking leverage in strategic competition without triggering overt military responses.

Unlike terrestrial infrastructure, undersea cables traverse enormous distances in remote ocean environments, making comprehensive monitoring and protection extremely difficult. They represent an asymmetric vulnerability — relatively easy to damage, enormously difficult to defend — that makes them attractive targets in both peacetime competition and conflict scenarios.

THREAT VECTOR ANALYSIS

Physical Sabotage

Undersea cables can be damaged or severed by specialized submarines or unmanned underwater vehicles (UUVs) operating in deep water far from observation. While accidental damage from fishing operations, ship anchors, and seismic activity remains the most common cause of cable outages, deliberate interference is increasingly considered a plausible and strategically attractive option for state actors. The ambiguity between accidental and intentional damage makes attribution difficult and provides cover for operations designed to deny responsibility.

Hybrid Warfare Below the Threshold

State and non-state actors may target communication infrastructure to disrupt economies, degrade military communications, and demonstrate capability without triggering the kind of conventional military response that a direct attack on territory would provoke. Such actions can remain below the threshold of open conflict — in the "gray zone" of modern strategic competition — while still achieving significant disruptive and coercive effects.

Intelligence Collection and Data Interception

Beyond physical damage, undersea cables are potential targets for intelligence gathering operations. Advanced state actors with deep-sea capabilities possess the technical means to access cable signal traffic for intelligence collection purposes. While cables typically carry encrypted data, the ability to intercept vast volumes of traffic provides value in long-term signals intelligence operations.

STRATEGIC ACTORS

Russia

Russia has demonstrated advanced deep-sea capabilities through its Main Directorate of Deep-Sea Research (GUGI), which operates specialized submarines and underwater vehicles designed for operations near critical seabed infrastructure. Russian vessels have been observed operating near major transatlantic cable routes on multiple occasions, raising concerns about reconnaissance and potential pre-positioning for sabotage operations.

China

China continues to expand its maritime and technological capabilities, including significant involvement in global cable infrastructure projects through state-linked companies. Chinese involvement in both cable construction and maintenance operations across Indo-Pacific routes raises potential dual-use concerns regarding intelligence access and physical vulnerability.

NATO and Western Response

NATO and allied nations are significantly increasing submarine surveillance, naval patrol operations, and infrastructure protection strategies — particularly in vulnerable regions such as the North Atlantic, Baltic Sea, and approaches to key European cable landing stations. The NATO Maritime Centre for the Security of Critical Underwater Infrastructure has taken a leading role in coordinating allied response planning.

GLOBAL IMPACT SCENARIO

A coordinated or significant disruption to undersea cable infrastructure would generate cascading effects across every sector of the global economy and security apparatus.

• Internet outages: Regional or global internet connectivity disruptions affecting hundreds of millions of users and critical services.
• Financial markets: Disruption to high-frequency trading, interbank settlements, and cross-border financial transactions, potentially triggering market instability.
• Military communications: Degradation of command and control networks that depend on civilian cable infrastructure as backup or primary communication channels.
• Cloud services: Major disruption to cloud computing infrastructure that underpins modern business operations globally.
• Psychological impact: Demonstration that critical global infrastructure is vulnerable creates broader deterrence and coercive signaling effects beyond the immediate physical damage.

DIPLOMATIC AND LEGAL SITUATION

There is currently no comprehensive international security framework specifically dedicated to protecting undersea cables from deliberate attack. The 1884 International Convention for the Protection of Submarine Telegraph Cables — one of the oldest multilateral treaties still in effect — addresses accidental damage and sabotage in criminal law terms, but lacks enforcement mechanisms for state-sponsored interference in modern geopolitical contexts.

International cooperation on infrastructure protection remains limited, constrained by intelligence sensitivities, attribution difficulties, and the reluctance of major powers to expose their own capabilities and vulnerabilities. Awareness of the issue is increasing among governments and within NATO, but translating awareness into effective protective measures remains a work in progress.

OUTLOOK

The most likely trajectory is increased focus on infrastructure security without immediate large-scale disruption, characterized by expanded monitoring and surveillance, development of rapid repair capabilities, increased military interest in subsea domains, and continued strategic ambiguity between accidental and intentional incidents.

Undersea cables are expected to become a central element of future hybrid conflict environments — a domain where the line between competition and conflict is deliberately blurred, and where the ability to threaten or damage critical infrastructure provides significant leverage in broader geopolitical negotiations.