Hundreds of subsea cables link up the worldwide web, with about a dozen connected to Australia. How does this little-known network work – and what happens if they’re sabotaged?

At the bottom of the freezing Sea of Okhotsk, deep inside Russian waters, a US submarine creeps into position. Navy divers emerge from a hatch they call “the Bat Cave” and sneak along the dark ocean floor, searching for a cable just centimetres wide on which they’ve planted a listening device – and, all the while, the Soviet fleet above is none the wiser.

It’s the 1970s and this is one of the most daring missions of the Cold War: wiretapping the secret communications cable between the Soviet fleet’s Pacific base and headquarters in Russia. The Soviets thought it so well guarded, in a heavily patrolled peninsula rigged with sound detectors, that most of what passed down that cable wasn’t even in code.

For a decade, US divers would return every month to retrieve the latest transmissions captured from their bug so analysts at the US spy agency the NSA could binge-listen to the juicy disclosures – from Soviet nuclear secrets to commanders’ conversations with their mistresses. Then, after yielding some of the most useful intelligence of the Cold War, Operation Ivy Bells came to a halt suddenly in the 1980s when a bankrupt NSA analyst quit his job and walked into the Soviet embassy to sell US secrets.

Above: Telstra crews connect the final stretch of a cable to shore.

A high-stakes Cold War wiretap under the sea might sound leagues away from our “wireless” world today. But the internet is not held in the “cloud” or beamed down by satellites – at least, not for the most part. More than 95 per cent of our data runs through a little-known network of undersea cables, each not much wider than a garden hose, stretching thousands of kilometres long.

While these cables are faster than satellites, some experts warn they are not well protected – and sabotage still happens. As Russia wages war in Ukraine and China expands into the private cable market, many countries are ramping up their underwater surveillance, including Australia.

How does the internet under the sea work? Can you tap a cable today? And what happens if they are snipped entirely?

What is the undersea internet network?

Right now, these words are likely travelling along the bottom of the ocean at close to the speed of light. Fibre-optic cables that transmit data as light are the superhighways on which the internet (and phone lines) travel between continents – they have much higher bandwidth than satellites and are specially reinforced to lie at the bottom of the sea, even resisting shark bites. Sci-fi writer Neal Stephenson once called them “Mother Earth’s motherboard”, and they were even entangled in the NSA surveillance scandal revealed by whistleblower Edward Snowden in 2013. A secret deal with US telco giant AT&T created the now infamous “Room 641A” at AT&T’s San Francisco site – behind its door, the NSA could tap cables coming up from the Pacific Ocean without a warrant.

More than 450 undersea internet cables crisscross the Earth, covering more than 1 million kilometres in total.

“Submarine cables have been the backbone of communications all the way back to the telegraph,” says former Australian intelligence official Dr William Stoltz at the ANU’s National Security College.

The first transatlantic cable was laid in 1858, connecting the US with Britain. Queen Victoria marked the occasion by sending a wire to US President James Buchanan – it took 17 hours to arrive. Things might be faster (and digitised) now, but the architecture is largely the same, Stoltz says.

More than 450 undersea internet cables crisscross the Earth, covering more than 1 million kilometres in total, and dozens more are planned. They can zap the equivalent of the United States’ entire collection in the Library of Congress across the other side of the world in moments. Australia is connected by at least a dozen cables itself, many of which land in Sydney and Perth.

In 1967, a British technician assembles one of the world’s early undersea cables in “clinic-like conditions” to stop dust being sealed inside.Credit:

Most of the world’s cables today still go through the US, although some nations, including those in South America and Europe, have been teaming up on routes bypassing the US, in light of the NSA spying scandal. There’s an even stronger move to bypass China and its tech giant, Huawei, long suspected of allowing backdoors for Chinese spies in its systems.

The only continent not plugged into the world’s undersea web is Antarctica, which relies entirely on satellites instead. Former Australian Antarctic station leader David Knoff likens operating without the subsea connections to “about 20 years ago, where you couldn’t watch movies, a short video clip would take an hour to download –occasionally it works but it’s a roll of the dice.” Some, including the Bureau of Meteorology, want Antarctica to get its own cable, as plans push ahead to lay lines beneath the freezing Arctic at the other end of the world.

“We don’t think about these cables, they’re out of sight at sea, but they’re vulnerable.”

But rolling out undersea cables is expensive and difficult. Almost all are privately owned and managed – often by consortiums of large telcos such as AT&T as well as, increasingly, the tech giants Google, Facebook (now Meta), Amazon and Microsoft. “Governments almost entirely rely on a handful of firms,” says Stoltz. “We don’t have our own sovereign capability to build, repair and inspect these things.”

Huawei Marine, now trading as HMN Technologies, has laid or repaired about 100, or almost a quarter, of the world’s cables. Google says it has invested in 22, including the newly launched 15,000 kilometre “Equiano” from Portugal to South Africa. Telstra owns a stake in 27 cables, more than 400,000 kilometres worth. “That’s the equivalent of going around the world 10 times,” says the chief of Telstra International, Oliver Camplin-Warner. “We’re the biggest provider inside Asia.”

He compares the undersea network to airline routes, following demand, “like London to Singapore”. Most people don’t realise the “magic” of how the internet works, he says. “They [often] think it just disappears up into the sky to a satellite.”

But you can wrap your hand around these cables – they are bundles of steel and copper and plastic, coated in petroleum jelly to help protect the delicate hair-thin optic fibres within. “They’re strong”, says Camplin-Warner, built today with “better armour” to withstand more extreme pressure as well as more sensors to detect disruptions.

Still, they are vulnerable – especially to natural disasters or stray boat anchors. Tonga is connected by just one subsea cable and at the start of this year, it was cut off from the world for more than a month when a volcanic eruption knocked out that line.

That’s why charting a new undersea cable route can take a year of planning. About 46,000 kilometres of new cable on average are installed globally each year – unspooled from specially fitted-out ships. “Picture almost a farmyard plough behind a tractor,” says Camplin-Warner. Near shore, “we bury the cable down into the seabed” for extra protection. Sensors on large ships set off alarms if they get too close. And Telstra uses an “Always On” system to near-instantly reroute internet traffic from one cable to another if there’s a problem. “The minute anything happens [our centres] know,” says Camplin-Warner. “We can tell how far the light [data] is travelling down the cable before it disappears so we can quickly work out exactly where the break is.”

Of course, the world’s small fleet of cable repair ships – those designed to haul up the damaged section of cable and splice in a new one – are also privately owned. “And there’s not enough,” says Anthony Bergin, a senior defence analyst at the Australian Strategic Policy Institute (ASPI). “It was weeks before a repair ship came out to Tonga and fixed their cable.”

A diver performs maintenance checks on a Telstra internet cable.Credit:Telstra

How secure are the cables?

With more of the world moving online – not to mention new underwater energy cables to export solar power and more – Bergin argues it’s time we took the security of all undersea cables more seriously. After all, you can find most on public maps. And, while there are still a few government cables off the books, Ivy Bells style, for more sensitive information, Stoltz says the vast bulk of agency intelligence worldwide travels along the same cables that carry your emails and Netflix shows.

Fortunately, data in transit is now generally safer than data “at rest” (on your computer) because most internet sites have begun using encryption as standard in recent years. Until emerging quantum computing advances enough to crack encryption, directly tapping undersea cables will remain “more of a Cold War thing”, Stoltz says. In the case of Ivy Bells, “the [US] knew what was being transmitted over those cables already, and so were able to isolate it”. In World War I, Britain snipped all of Germany’s undersea cables save one, which they listened in on.

But today, so much information is zipping around the world, all scrambled up in packets of data and then reassembled at the other end, that siphoning off useable intelligence “would still be like trying to find a needle in a million haystacks”, Stoltz says. There’s too much noise.

“But that’s not to say that in a war, you wouldn’t just go and cut all your enemy’s cables. You could sever a country from the internet”, knocking out their banking, business, health networks and more, “and it would take potentially months to repair”. Unplugging a nation before attack now features in most country’s war plans. “Any modern military worth its salt is investing in these sorts of technologies”, says Stoltz.

In 2016, “the idea that you could reliably land a cable in Hong Kong and feel confident that it wouldn’t be tapped into was still a viable idea.”

Meanwhile, nations still go hunting for each other’s secret cables too, in the hopes the isolated line might yield Ivy Bells-style rewards. In the ’70s, innocuous Russian signs warning local fishermen away from cables is how the Americans found that guarded Soviet line in the first place.

But the key vulnerability is where cables land on shore – inconspicuous buildings known as landing stations. Hackers could take control of the physical systems that manage the cables there or plant a bug “and we’d be none the wiser,” says Bergin. “Power could be cut to those sites, explosives detonated. There could even be missile strikes.“(Earlier this year, US officials foiled hackers probing access to a landing station in Hawaii, one of the world’s major cable landing hubs.)

Above: A shark bites a Google-owned cable in the Pacific. Google now uses Kevlar to reinforce its cables. Source: YouTube

Australian laws criminalising interference with cables are among the best in the world, Bergin says, creating protection zones around landing stations, but they only extend so far. Beyond our territorial waters, they can’t protect our traffic. And experts say current international laws fall well short.

“Of course, whether you actually have a presence around our landing sites to make sure they’re not interfered with is kind of an open question too,” Stoltz says. “Australia doesn’t have a Coast Guard, for example.”

Where it can, “Australia advocates” for overseas agreements to align with its own cable protections, a federal government spokesman said, but would not comment on “operational matters” related to how cables are secured.

Meanwhile, experts warn that some countries may have found a more subtle means of interfering with cables – via alleged inbuilt backdoors and plants in the wires themselves. Huawei, which is founded by a former officer in China’s People’s Liberation Army, denies allowing the Chinese government access to its user data and systems, saying that would be “corporate suicide” considering its international business interests. It claims that overseas network operators using Huawei still have security control.

The company has been repeatedly linked to allegations of espionage, hacking and data theft, including the bizarre case of data transferred every night on the stroke of midnight from the African Union headquarters it helped build to unknown servers in Shanghai. Just in October, Chinese spies were arrested in the US accused of trying to interfere with the States’ criminal investigation into Huawei.

Many Western countries, including Australia, have now banned the company from involvement in their 5G networks, and US sanctions on Huawei have sunk some plans to land undersea cables in Hong Kong by companies such as Google and Meta.

Kurt Tong, a former US diplomat in Asia, recalls when he arrived in Hong Kong as the US head of mission in 2016, before the introduction of sweeping national security laws across China, “the idea that you could reliably land a cable in Hong Kong and feel confident that it would not be improperly tapped into was still a viable idea”. “By the time I left … things felt differently.”

In 2018, Australia stopped Huawei from laying a submarine cable between Sydney, and the Solomon Islands and Papua New Guinea, agreeing to help fund the venture itself. And last year, the World Bank cancelled a cable contract in the Pacific over fears Huawei would win the tender.

It’s part of fierce “cable diplomacy” now playing out in the Pacific, Bergin says, as Australia and the US vie with China for influence on the developing islands. But it’s also a larger battle for control of the world’s growing communication networks, and both China and the US are seeking an intelligence advantage. Stoltz wonders if we’re starting to see the “international technology ecosystem split in two”.

But how hard is it to snip cables – and would it mean war?

It’s not easy. You’ll likely need a submersible, for one, although it has been tried without – three divers in a fishing boat were caught cutting a cable off Egypt in 2013. “But you feel it’s not just somebody swimming down there with a pair of scissors,” quips Tong. “It’s more complicated than that.”

During Operation Ivy Bells, for example, US divers had to wear special suits to avoid freezing in the icy Russian waters or getting the bends in the crushing depths where the cable lay. Once, when a sudden storm hit the waters above, Captain James Bradley took the risky move of partially flooding the submarine to stop it rising to the surface – and being exposed to the Soviet forces there.

The New York Times has reported that today the United States’ advanced submarine the USS Jimmy Carter can tap undersea cables via a special compartment that allows engineers to bring a cable up inside. Russia and China are also believed to have the undersea tech, from specialist submarines to drones, capable of interfering with cables, and their “research” or “fishing” vessels have been spotted tracking cables around the world.

Even before the war in Ukraine, NATO leaders were discussing how best to protect undersea cables from Russian sabotage. In January, a cable connecting Norway’s Arctic islands of Svalbard to the rest of the world was mysteriously snipped. And the UK’s military chief warned Russia that any attempt to cut its own cables could be considered an act of war.

“Severing a submarine cable, that’s really the nuclear option.”

Now, with Russian sabotage blamed for holes blown in the Nord Stream gas pipelines that ferry energy to Europe, fears of further undersea damage are ramping up. Already, France’s land internet cables and those controlling Germany’s train lines have been deliberately cut by saboteurs unknown. “If energy pipelines can be interfered with, people are saying, ‘Are undersea internet cables next?’” Bergin says.

Cyber warfare, for the most part, has lingered in the “grey zone” between peace and war. “But severing a submarine cable, that’s really the nuclear option,” says Stoltz. There could be serious human cost. And, while it might be hard to trace back to a state, as cyberattacks are, he says the risk of being caught would be high for peacetime. “You’d really only do that if you’d already decided to go to war. Russia, as it’s starting to get towards the nuclear threshold in its war in Ukraine, that’s when it’s starting to also do these sorts of things, [attacking] Nord Stream.”

Of course, for smaller nations severely outgunned by aggressor countries (such as Nordic states near Russia), Stoltz says cable sabotage may yet be used short of war, “for example, if China wanted to cut off Taiwan from the rest of the world, and strangle them into submission”.

Whether other nations could intervene to defend a smaller nation from such an attack is unclear. But the old assumption that cyberattacks won’t trigger physical retaliation no longer stands, he says. ” Our society is so networked now. It could escalate very quickly to [war].”

An underwater volcanic eruption and subsequent tsunami left Tonga strewn with debris and without its submarine internet cable for weeks.Credit:Australian Defence Force

How are we protecting cables? What happens if they’re cut?

The federal government did not answer questions on how it would respond to cable sabotage but said the telecommunications industry had a long history of redundancy planning. Unlike Tonga, Australia has many cables connecting it beneath the waves and Telstra, which owns 10 of them, says it could re-route data along its remaining ones if some are knocked out.

“The best-case scenario is that the internet slows down,” says former intelligence and defence official Marcus Hellyer at ASPI. But if Australia is cut off entirely, much of our digital world – from Netflix to the stockmarket – will collapse.

We’d need to switch to satellites fast – so access to the rapidly deployable kind, such as Elon Musk’s Starlink internet (now used in besieged Ukraine) or the kits Telstra sometimes sends to areas of Australia hit by fire or flooding, will be essential, Stoltz says. Even then, communications would have to be triaged (as was the case in Tonga where Telstra and the Australian government helped restore emergency communications via satellite). “You can’t go from our normal internet traffic and push it entirely on to satellite bandwidth,” Stoltz says. “They’re really only an emergency solution, short term.”

It’s why, despite advances in satellites helping connect more remote parts of the world, no one expects submarine cables to be ditched any time soon. And why developing nations need an affordable alternative to China’s “cable diplomacy”, Stoltz and Bergin say.

“For countries, particularly in South-east Asia and the Pacific, that really do rely on these big foreign telcos building this infrastructure … it’s a tension between security and economic development,” Stoltz says. “They’re the ones in the middle that we’re jostling over.”

The South China Sea is not only a tangle of disputed maritime and island claims but a “cable chokepoint” for the network.

Tong says some developing nations have a different perspective on the West’s security concerns. “I don’t think they really care if China’s reading their emails.” China is a huge economy, so cable connections to it “absolutely should” and will continue, he says. But he adds: “I think over the years people have felt a bit better about security if they are sending data transmission from Japan to Australia, for example, directly … than having it land in China first and then be transmitted.”

That’s partly why new hubs are opening up in places such as Singapore and Korea. Camplin-Warner says Australia itself is becoming an important data landing site between the US and Asia, even though “it may not be the quickest route”. One of Australia’s newest cables, Southern Cross NEXT, (which Telstra has a 25 per cent stake in) runs straight to the US, the first direct route between the continents.

Taiwan is another emerging hub, despite the tricky geopolitics, Camplin-Warner says.

And nearby, the South China Sea is not only a tangle of disputed maritime and island claims but a “cable choke point” for the network. As researcher Lane Burdette writes for Princeton University, many nations rely on cables running through those waters, but China’s build-up of artificial islands there appears to use cables that aren’t made public. And some experts fear Beijing may yet move to block or control cables and their repairs in the region.

Meanwhile, if China were to cut Taiwan’s undersea cables, sometimes described as the island’s Achilles’ heel, the impact would be felt nearby too – it’s connected by a dozen cables to countries including Australia, Singapore, Japan and the US.

In 2017, Rishi Sunak, now Britain’s prime minister, outlined a case to ramp up the defence of these “jugulars of the world economy”, including that the government install more back-up “dark cables” itself.

As another island, Australia is particularly vulnerable too, Bergin says. Yet, while the new AUKUS technology-sharing partnership with the US and the UK means greater investment in undersea capability, there’s been no focus on maritime infrastructure security.

Australia is already bringing in minimum cybersecurity standards on privately-owned critical infrastructure – including undersea internet and energy cables. And, unlike voluntary reforms in the US, it’s hoped they will have teeth. The government spokesman didn’t say how the standards will be monitored beneath the waves but said it worked closely with companies, which have “obligations to do their best to protect networks from unauthorised access and interference,” and to report breaches. The security of internet cable projects, including landing sites, is assessed when companies seek a permit to operate from their day-to-day regulator Australian Communications and Media Authority (ACMA), which also oversees repairs, the spokesman said.

At Telstra, Camplin-Warner says “security is absolutely paramount”. The telco has previously worked with Australia and other governments to bring in protected exclusion zones around landing stations, he says, and Telstra is seen as a “safe, neutral provider internationally”. “We don’t have any Huawei equipment in our network.”

Meanwhile, defence expert Malcolm Davis says Australia is investing in better tech to hunt submarines, as China tries to close the gap between its own navy and America’s. “We haven’t faced a threat like we do today in the region. The Soviets rarely sent submarines this far south.”

The federal government spokesman said a new maritime undersea combat and surveillance program was created in late 2021, with $7.4 billion for an “Integrated Undersea Surveillance program”. The Australian navy has already flagged the plans for “ocean surveillance ships”, undersea drones and sensors, and the latest October budget papers reveal $155 million in funding earmarked over the next financial year to buy an “undersea support vessel”.

Still, in the end, the best defence may be mutually assured destruction, says Hellyer. “Everyone will start cutting cables if there’s a war, but you can’t be everywhere in the ocean. We might need an agreement, [rules of law], not to touch this kind of critical infrastructure. Because once we start …”.

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