Invisible highways: Undersea Cables Power 99% Of Global Internet Traffic, Despite Growing Risks

The world’s digital economy depends heavily on a vast network of undersea cables stretching across the ocean floor, quietly carrying nearly all international internet traffic and enabling trillions of dollars in financial transactions every day.

Despite their central role in modern connectivity, these cables remain largely invisible to the public, even as governments and technology experts grow increasingly concerned about their security and resilience.

Tomas Lamanauskas, Deputy Secretary-General of the International Telecommunication Union (ITU), highlighted the importance of the infrastructure ahead of a global summit on submarine cable resilience in Porto, Portugal.

“About 99 per cent of the international internet traffic goes through submarine cables. Even the conversation you and I are having right now is carried through these cables,” he said in an interview with UN News.

Backbone Of The Digital Economy

While most people associate internet access with mobile networks, satellites or broadband connections, the global exchange of data actually relies on a complex system of fibre-optic cables lying hundreds of metres beneath the ocean surface.

These cables act as the “digital highways” of the modern world, linking continents and enabling the rapid movement of information across countries and markets.

Today more than 500 commercial submarine cables connect different parts of the world, carrying vast volumes of data every second. Together, they stretch across roughly 1.7 million kilometres of ocean floor, long enough to circle the Earth multiple times.

Though relatively thin, roughly the width of a garden hose, the cables transmit hundreds of terabits of information per second using fibre-optic technology.

A Technology With Deep Historical Roots

The idea of connecting nations through underwater cables dates back more than a century.

The first undersea telegraph cable was laid between England and France in 1850, marking the beginning of a technological transformation in global communications.

Over time, these systems evolved from telegraph lines to telephone networks and eventually to high-speed fibre-optic cables capable of transmitting massive volumes of digital data.

Before cables are installed, engineers survey the seabed to identify routes that minimise environmental impact and reduce the risk of damage. Specialised ships then deploy the cables, unrolling large reels onto the ocean floor.

Disruptions Can Have Global Impact

Because submarine cables form the backbone of international communications, any disruption can quickly affect economies, financial markets and essential services.

According to the ITU, between 150 and 200 cable incidents occur globally each year, averaging three to four disruptions every week.

Some of the most significant disruptions in recent years occurred in the Red Sea, where cable damage in 2024 interrupted roughly a quarter of data traffic flowing between Europe and Asia.

Outages can also be triggered by natural disasters such as earthquakes, underwater landslides or volcanic eruptions.

However, experts say human activity accounts for the majority of incidents. Around 80 percent of cable damage is caused by fishing trawlers or ship anchors dragging across the seabed.

Remote Regions Face Greater Risks

When cables fail, the consequences can be particularly severe for remote island nations and regions with limited connectivity.

Lamanauskas pointed to the Pacific island nation of Tonga as an example. Since 2019, the country has experienced three major internet disruptions linked to an earthquake, volcanic eruptions and accidental damage caused by ship anchoring.

In areas with only a single cable connection, even minor damage can leave entire populations without internet access for days or weeks.

“Imagine your entire community being offline for a week, unable to access digital healthcare, information or education,” he said.

Even small delays in data transmission can have significant economic consequences. For instance, a millisecond delay caused by cable congestion could affect financial trading systems in major global markets.

Repairs And Maintenance Challenges

Maintaining the vast network of undersea cables presents logistical challenges.

Some of the infrastructure installed during the early 2000s technology boom is now nearing the end of its typical 25-year lifespan, increasing the need for maintenance and replacement.

When a cable is damaged, engineers can usually identify the problem quickly using monitoring systems. However, the repair process often involves complex international coordination.

Obtaining permits and approvals from multiple jurisdictions can sometimes delay repair operations more than the technical work itself.

Depending on the location of the damage and the availability of specialised repair vessels, restoring a cable may take anywhere from several days to several months.

Global Efforts To Strengthen Cable Resilience

The growing dependence on digital connectivity has prompted governments and industry leaders to focus more closely on protecting submarine cables.

The International Telecommunication Union is working with countries and private companies to strengthen the resilience of the global network.

Its efforts include developing technical standards, improving coordination between countries and encouraging faster permitting processes for repairs.

The agency also promotes measures to prevent accidental damage and ensure that cable maintenance can be carried out more efficiently.

Lamanauskas said the rapid expansion of internet use continues to drive massive growth in cable capacity.

“Over the last 40 years, the capacity of these optical cables has been increasing by about 40 per cent every year,” he said, describing the growth as exponential.

As global demand for data continues to surge, strengthening the reliability and security of these underwater connections will remain a critical challenge for governments, businesses and international organisations alike.