Risk Beneath the Waves
Safeguarding Subsea Cables for a Secure Global Network
By Romina Bandura, Erin Murphy, and Thomas Bryja
Risk Beneath the Waves
Safeguarding Subsea Cables for a Secure Global Network
By Romina Bandura, Erin Murphy, and Thomas Bryja
Fiber-optic subsea cables are critical to meeting the unprecedented demand for data in the cyber age.
With the global demographic and technological shifts currently underway, this infrastructure will become even more important in the coming decades, as more people than ever before access and depend on the internet.
Massive investments in energy systems, digital infrastructure, and other supporting capabilities will be required to meet this demand. Greater resources for protecting and repairing these vital networks will also be essential for the continued security of internet infrastructure.
Workers lay the 2Africa submarine cable at Barcelona Cable Landing Station (CLS) in Spain. | David Oller/Europa Press via Getty Images
Workers lay the 2Africa submarine cable at Barcelona Cable Landing Station (CLS) in Spain. | David Oller/Europa Press via Getty Images
However, geopolitical tensions and worldwide competition for technological leadership are intensifying. The risks facing critical infrastructure, including subsea cables, have never been higher.
Meeting these challenges requires complex and coordinated action, which cannot be achieved without understanding the indispensable role these cables play in the digital era, as well as their potential vulnerabilities.
The Importance of the Network
The structures facilitating digital connectivity may now be considered critical infrastructure, just like water, energy, and transportation infrastructure. Subsea cable systems foster societal cohesion, enable economic growth, and safeguard national security.
$10 trillion
Some estimates value financial transactions carried by subsea cables at $10 trillion globally per day.
The digital connectivity that these cables provide cannot be substituted by satellite technology, which is far more costly, has reliability concerns, and carries much less information per second.
Often described as the backbone of the internet, this infrastructure is becoming even more critical as global demand for connectivity accelerates. As demand increases, so too does the need for stable connectivity and additional subsea cables.
Several converging trends are driving bandwidth needs to historic heights:
1. Rapid expansion of AI and growth of data centers
AI applications and the data centers critical to their operation are proliferating globally. These systems often depend on the cross-border movement of data, requiring ever better connectivity via subsea cables.
2. Regional demographic changes
Populations are booming across Africa and Southeast Asia, resulting in higher demand for internet access within and among in the Global South.
3. Rising geostrategic challenges
Russia's war in Ukraine and heightened tensions in the Taiwan Strait have illustrated the vulnerability of subsea cables, particularly in the context of great power competition.
Taken together, these trends underscore the ascendant strategic necessity to ensure resilient and secure cable networks.
The Subsea Cable Threat Ecosystem: Vulnerabilities and Challenges
Cable damage is common: On average, there are 200 cable faults annually, mainly due to fishing and commercial vessels dropping or dragging anchors. This rate has remained steady for the last decade. It can take two to eight weeks to repair a cable fault and, in the worst instances, far longer. Estimates vary, with an average minimum cost of $500,000–$1,000,000 per repair.
Several threats and challenges compromise the integrity and functioning of these networks.
Physical Vulnerabilities
Cables can be cut due to any of the following reasons:
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Accidents from human activities
Fishing and anchor dragging account for 70 percent of all cable damage.
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Environmental and natural disasters
Earthquakes, storms, underwater landslides, hurricanes, and volcanic eruptions disrupt both underwater networks and landing stations. These accounted for 25 percent of cable damage between 1965 and 2019.
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Intentional disruption by state or non-state actors
Instances of sabotage of subsea cables, as part of gray zone operations or hybrid warfare tactics, are difficult to document and quantify due to their deniable nature, and even potential cases are quite limited compared to faults due to accidents and natural disasters. Regardless, cable systems remain vulnerable to the possibility of physical sabotage.
Nonphysical Challenges
These challenges compromise network redundancy and resiliency:
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Bureaucratic obstacles
A tangled patchwork of laws, regulations, permitting procedures, and cabotage rules lead to lengthy, sometimes multiyear, approval processes with changing standards and timelines. These factors deter investment, slow expansion of capacity, limit network redundancy and resiliency, and lengthen the repair time for damaged cables.
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Outdated regulatory structures and nonbinding international frameworks
While the Federal Communications Commission has made some revisions, much of the foundational U.S. regulatory structure on subsea cables hasn’t been comprehensively modernized in over 100 years, since the Cable Landing License Act of 1921 and the Submarine Cable Act of 1888 before that. Internationally, other laws and frameworks lack consistent global enforcement, protection, and punitive measures for damaging cables.
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Limited repair and cable-laying capacity
A shortfall in the number of purpose-built vessels worldwide delays laying and repairing subsea cables.
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Structure and concentration of cable ownership
Authoritarian state ownership of cable production, cable-laying ships, and networks may expose host countries to strategic and operational vulnerabilities.
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Lack of cooperation and dialogue
Public and private sector misalignment about the threats, challenges, and priorities in this sector delays repair and further investment.
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Limited budgets
Government funds for the protection and added resiliency for cables are limited.
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In reality, cables often face challenges from not one but several of these intersecting threats, making enhanced protection and resiliency critical to sustaining these networks.
Insights from Recent Incidents
Recent incidents illustrate the various types of threats to global communications infrastructure, how they overlap, and their complex, often devastating impacts.
Impacts of Cuts
Damage to and delays in repairing or building new cables can have far-reaching impacts.
The immediate impact for users is a disruption in communications, including difficulty connecting to the internet or slow service, missed phone calls, and problems with messaging apps.
However, the impacts of damage to subsea cables can be more far-reaching and dangerous, on a personal and national level.
Socioeconomic Impacts
Internet
Banking
Finance
E-government
Transportation
Health systems
Communication
Commerce
When two subsea cables providing internet to Taiwan’s island of Matsu were cut in 2023, user communication was heavily impacted. Text messages took hours to send, if they went through at all, and videos were unwatchable. Moreover, banks had challenges processing financial transactions on time, impacting businesses and individual customers.
Other services that rely heavily on communication cables include e-government (e.g., payment of taxes and wages to civil servants), transportation (e.g., grounded flights and bus routes), and health systems (e.g., scheduling of patients and surgeries).
The societal effects of cuts compound with economic losses. Although the economic impacts from subsea cable damage are difficult to quantify and vary based on the connectivity of the country and severity of the disruption, some estimates place the financial loss at more than $1.5 million per hour.
A cut of undersea cables in Nigeria and neighboring countries in March 2024 led to millions of people across Africa losing internet services for up to four days. The incident cost the Nigerian economy close to $600 million, and banking institutions reported having difficulties providing online services to their customers.
Distinguishing between the impacts on highly digitalized economies and those that are less digitalized, Deloitte estimates that a temporary shutdown of the internet would cost a highly connected country $23.6 million on average for every 10 million people per day. By comparison, countries with medium connectivity would face losses of $6.6 million in daily costs per 10 million people, while those with low connectivity would incur approximately $0.6 million per day.
This combination of economic and social implications elevates cable redundancy, resiliency, and repair to a political and financial imperative in the modern age. However, subsea cables are not merely conduits of data—they also underpin national security.
National Security Impacts
Systemic risk
Sensitive communication disruption
Data collection
Sabotage
Cable damage can easily escalate into national security threats. The design and structure of a cable network can introduce systemic risk, as a single incident may disconnect an entire small country from global communications or cause significant delays.
This vulnerability is especially relevant for countries such as small nations or island states that lack redundancy (i.e., spare capacity) in their networks and for which building additional cables is not commercially viable for the private sector or not feasible due to space constraints for cables to land. Furthermore, if cables are concentrated in a particular area due to limited space or routing options, these risks are magnified, as it is easy to damage several cables at one time.
For example, when Taiwan’s Matsu Islands experienced cable cuts in February 2023, its residents were plunged into near-total digital isolation. Island residents relied on microwave radio transmission to send small amounts of data.
Fishermen on a jetty at a harbor on Beigan island in Taiwan’s Matsu archipelago. | Jack Moore/AFP via Getty Images
Fishermen on a jetty at a harbor on Beigan island in Taiwan’s Matsu archipelago. | Jack Moore/AFP via Getty Images
Because subsea cables carry all types of information, including sensitive data and governmental communications, policymakers are increasingly particular about the vendors who build and repair these cables, as well as the technology within landing stations. Some in government agencies fear that components of submarine line terminal equipment—used to translate the optical signals flowing through the subsea cables into readable data—could clandestinely siphon off information for a bad actor. Private sector experts have been dismissive of the idea, however, noting the computational infeasibility of grabbing such massive sums of encrypted data and using it for any sort of useful espionage purposes.
Finally, malign actors could intentionally target maritime infrastructure as a gray zone tactic to cause societal, economic, or security disruptions. Although these types of cuts are rare and difficult to prove, they invite diplomatic or even military crises in tense geopolitical environments. Of course, in an active wartime scenario, communication infrastructure such as subsea cables may be among the first targets to be destroyed, as has been the case since World War I, when England’s opening action was to cut Germany’s submarine telegram cables.
Given the societal, economic, and national security importance of cables—and the threats they face—greater emphasis must be placed on their protection, repair, and redundancy.
Securing Subsea Cable Infrastructure
The global nature of communications infrastructure requires action and coordination among many different stakeholders, at both the national and international levels.
Public Sector
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National level
Governments must raise subsea cables to a national security priority and pursue efforts to streamline permitting and regulatory processes, clarify project approval timelines, and aid engagement with the private sector, including by designating a single responsible agency or point of contact.
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International level
Maritime treaties and frameworks must be updated to reflect contemporary realities, while ensuring that coastal states are held accountable for enforcing relevant laws and ensuring perpetrators face real consequences for the activities of vessels bearing their flag.
Private Sector
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Partnership
The private sector—including cable manufacturers and the major companies driving global data usage—should engage proactively with governments to align commercial and security priorities, ensuring that infrastructure development and protection efforts are mutually reinforcing.
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Technology
Leveraging new technologies, such as sensors, drones, and unmanned underwater vehicles, is critical to enhancing detection and deterrence in the protection of this vital infrastructure.
Donors
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Donor nations
Donor nations can provide technical support to nations lacking the legal or bureaucratic capacity to protect subsea cable infrastructure. They can also help finance strategically important cable projects in emerging markets that may not be commercially viable but are crucial for global connectivity and geopolitical stability.
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Development finance institutions
Development finance institutions can offer debt and equity financing along with technical assistance and de-risking mechanisms to support cable projects, particularly in emerging markets where investment risks are higher or projects are not commercially viable.
Both the public and private sectors need to enhance information sharing and collaboration to better understand their respective threats, address challenges, and implement actions for subsea cable protection. Donors also have a key role to play. These and other measures will help enable a digital future that is more secure, resilient, and accessible.
Conclusion
The world’s global communications infrastructure looks very different today than it did 170 years ago when the first transatlantic underwater cable was laid. In the coming decade, the importance of this infrastructure will continue to grow.
The AI revolution, accelerating technological competition, demographic shifts, and rising geopolitical tensions have made the modern world both uniquely dependent upon these systems and vulnerable to their disruption.
Because subsea cables remain vulnerable to a wide range of threats and challenges, elevating and protecting this critical infrastructure is vital. This requires a clear understanding of the global economic significance of subsea cables, as well as a careful assessment of their vulnerabilities and the challenges faced by both public and private stakeholders.
Ultimately, developing and implementing effective safeguards will be essential to mitigating risks to this infrastructure and shepherding a more resilient digital future.
This report has been made possible by the generous support of Amazon Web Services (AWS), Computer and Communications Industry Association (CCIA), and Kuwadate Inc.
Dedicated to the memory of H. Andrew Schwartz, who championed this project and countless others.
Research
The CSIS Project on Prosperity and Development:
WRITTEN BY:
Romina Bandura, Senior Fellow
Thomas Bryja, Program Manager and Research Associate
Erin Murphy, former deputy director and senior fellow for the Economics Program
ACKNOWLEDGEMENTS:
Special thanks to all the experts who generously provided their insights in roundtable discussions and interviews to inform our reports over the past 18 months.
Story Production
The Andreas C. Dracopoulos iDeas Lab:
EDITORIAL & PROJECT OVERSIGHT:
Sarah B. Grace
DESIGN BY:
Shannon Yeung
Gina Kim
Sarah B. Grace
DEVELOPMENT BY:
José Romero
MAP VISUALS & DEVELOPMENT:
Fabio Murgia
COPYEDITING BY:
Hunter Macdonald
Phillip Meylan
Madison Bruno
Photo Credits
Cover
Coral reef overlay | Modifications to image by Inna via Adobe Stock; Subsea fiber-optic cable | Shannon Yeung/CSIS; Seabed with rocks | Modifications to image by imaginima via Getty Images.
Backgrounds
Threat Ecosystem: Seabed with rocks | Modifications to image by imaginima via Getty Images.
Conclusion: Close-up of optical fibres | Viorika via Getty Images.
Trends:
Rapid expansion of AI and growth of data centers: Construction at the first Stargate AI data center created by OpenAI, Oracle and SoftBank in Abilene, Texas, in 2025. | Kyle Grillot/Bloomberg via Getty Images.
Regional demographic changes: People in Bangkok hold up flashlights on their mobile phones during a concert. | Matt Hunt/SOPA Images/LightRocket via Getty Images.
Rising geostrategic challenges: Energy and utility workers operating to restore power and heat supply after a Russian drone strike on a residential area on December 27, 2025 in Kyiv, Ukraine. | Yevhenii Zavhorodnii/Global Images Ukraine via Getty Images.
Impacts:
Socioeconomic Impacts:
Internet: Person typing on gray and black HP laptop. | Benjamin Dada via Unsplash.
Banking: A building with an ATM sign lit up at night, | Jake Allen via Unsplash.
Finance: A monitor shows market trends, | Nick Chong via Unsplash.
E-Government: A government building at night. | Michael via Unsplash
Transportation: A train arrives in Berliner Tor station in Hamburg, Germany. | Jonas via Unsplash
Health systems: A hospital room in the National Cancer Institute. | National Cancer Institute via Unsplash
Communication: A hand holding a smartphone shows a messaging app | Ice Family via Unsplash
Commerce: Cargo containers are loaded at a port. | Lucas van Oort via Unsplash.
National Security Impacts:
Systemic risk: A crowded train and bus station in Switzerland. | Claudio Schwarz via Unsplash.
Sensitive communication disruption: A red telephone sitting on top of a table. | Mike Gattorna via Unsplash.
Data collection: A security camera. | Alex Knight via Unsplash.
Sabotage: Network internet cable is cut using shears. | Klmax via Getty Images.
Conclusion: A DSLR close-up photo of fiber optics in blue tones. | Viorika via Getty Images.
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