What lies beneath: the growing threat to the hidden network of cables that power the Internet

it was the opening days of 2022, in the aftermath of a huge volcanic eruption, when Tonga went dark. The underwater blast – 1,000 times more powerful than the bomb dropped on Hiroshima – sent tsunami waves across the nearby archipelago of Tonga and covered the island’s white coral sand in ash.

The power of the Hunga-Tonga-Hunga-Ha’apai eruption disrupted the Internet connection to Tonga, causing a communications blackout just as a crisis was unfolding.

When the submarine cable that supplies the country’s internet was restored weeks later, the scale of the disruption was clear. The lack of connectivity had hampered recovery efforts while at the same time destroying businesses and local finances, many of which depend on remittances from abroad.

The disaster exposed the extreme vulnerability of the infrastructure that supports the operation of the Internet.

Modern life is really inseparable from an operational Internet, says Nicole Starosielski, a professor at the University of California, Berkeley and the author of The Undersea Network.

In that way, it’s a lot like drinking water—a utility that supports our existence. And like water, very few people understand what it takes to travel from a distant reservoir to our kitchen faucets.

Modern consumers have come to imagine the Internet as something invisible in the atmosphere—an invisible “cloud” just above our heads, raining data down on us. Because our devices are not connected to cables, many of us believe that the whole thing is wireless, says Starosielski, but the reality is much more extraordinary.

Almost all Internet traffic—including Zoom calls, movie streams, emails, and social media feeds—reaches us through high-speed fiber optics laid on the ocean floor. These are the veins of the modern world, stretching almost 1.5 million km under the sea, connecting countries through physical cables that funnel the Internet through them.

Speaking via WhatsApp, Starosielski explains that the data her voice sends will travel from her cell phone to a nearby cell tower. “That’s basically the only wireless hop in the whole system,” she says.

From the cell tower it will pass through a set of terrestrial fiber optic cables, traveling at the speed of light underground. It will then go to a cable landing station – usually somewhere near the water – and from there to the bottom of the seabed, before emerging at a cable landing station in Australia, where the Guardian spoke to Starosielski.

“Our voices are literally at the bottom of the ocean,” she says.

Spies, sabotage and sharks

That the data that powers financial, government and some military communications, cables run not much thicker than a hose pipe and protected by little more than the seawater above them, has become a cause of concern for lawmakers around the world in recent years .

In 2017, NATO officials reported that Russian submarines had stepped up their surveillance of Internet cables in the North Atlantic, and in 2018 the Trump administration sanctioned a Russian company that allegedly provided Moscow with “underwater capabilities” aimed at monitoring the underwater network.

A Russian attack on undersea cables would “cause significant damage to our economy and to our daily lives,” said Jim Langevin, a member of the US House Armed Services Committee.

Targeting Internet cables is a weapon Russia has long held in its arsenal of hybrid warfare. When Russia annexed Crimea in 2014, Moscow cut the main cable link to the peninsula, gaining control of its internet infrastructure, allowing the Kremlin to spread disinformation.

Global conflicts have also been shown to have unintended, disruptive effects on Internet cable systems. In February, Iranian-backed Houthi militants attacked a cargo ship in the Red Sea. The eventual sinking of Ruby Lake was likely responsible for severing three submarine cables in the region, disrupting a significant portion of Internet traffic between Asia and Europe.

The US and its allies have also expressed serious concerns that adversaries could tap into the submarine cables to obtain “personal information, data and communications”. A 2022 congressional report on the issue highlighted the increased potential of Russia or China to gain access to the undersea cable systems.

It’s a method of espionage with which the US is all too familiar: in 2013 the Guardian revealed that the UK’s GCHQ had tapped into the network of internet cables to gain access to vast amounts of communications between completely innocent people as well as targeted suspects. This information was then passed on to the NSA.

The documents, revealed by whistleblower Edward Snowden, also showed that an undersea cable connecting Australia and New Zealand to the US was tapped to allow the NSA access to Australian and New Zealand internet data.

Despite the variety of dangers and the increasingly vocal warnings of Western governments, calls for greater action in securing the cable network have gone largely unanswered and many see the threats as overblown.

“There are no publicly available and verified reports indicating deliberate attacks on the cable network by any actor, be it Russia, China or a non-state group,” a 2022 EU report said.

“Perhaps this means that the threat scenarios being discussed may be exaggerated.”

One expert who spoke to the Guardian was blunter in his assessment, describing the threat of sabotage as “bullshit”.

The data bears this out, showing that sharks, anchors and fishing pose a greater threat to the global internet infrastructure than Russian spies. An American report on this problem showed that the major threats to the network are “accidental incidents with people”. On average, a cable is broken “every three days”.

“A submarine telecommunications cable was accidentally severed by a ship off the coast of Somalia in 2017, leading to a three-week internet outage costing the country $10 million per day,” the report states.

An uneven internet

For many experts, however, the greatest risk to the Internet is not sabotage, espionage, or even rogue anchors—but the uneven distribution of the cable infrastructure that runs across the globe, connecting the world’s digital networks together.

“There aren’t cables everywhere,” says Starosielski. “There is a concentration in the North Atlantic connecting the United States and Europe, but there are not as many in the South Atlantic.”

“So you see some parts of the world have a high level of connectivity … and diversity in terms of multiple routes in case there’s a breach.”

As of 2023, there were more than 500 communication cables at the bottom of the ocean, but a quick look at the map of the world’s undersea cable networks shows that they are mostly centered around economic and population centers.

The uneven distribution of cables is most obvious in the Pacific Ocean, where a territory like Guam, with a population of only 170,000 and which has a US naval base, has more than 10 internet cables connecting to the island. New Zealand, with more than 5 million people has seven. Tonga has only one.

In the aftermath of the 2022 eruption in Tonga, governments around the world were sprung into action, filing reports of vulnerabilities in the existing undersea cable network, while tech companies worked to strengthen networks to ensure that n event never happened again.

Last month Tonga’s internet went down again.

Huge swaths of the country were left in the dark after the undersea internet cable connecting the island network was damaged, causing chaos for local businesses.

For now, the economic foundations for building more cables are across the Western world and in emerging markets, where digital demand is booming. Despite the warnings of sabotage or accidental damage – experts say that without the imperative to make the market more resilient networks, the real risk is that places like Tonga will remain dark, threatening the very promise of digital equity that the Internet was founded on.