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Undersea cables explained: what Iran's threat to the wires under Hormuz means for India's internet
A senior Revolutionary Guards commander said this week that the internet cables beneath the Strait of Hormuz could be destroyed if Iran is attacked. How these cables work, how much of India's traffic uses them, and what would happen if they were cut.
The short answer
Almost all international internet traffic travels through fibre-optic cables laid on the seabed, not via satellites. Several cable systems linking the Gulf states with India, Europe and Africa run through the Strait of Hormuz, and on 21 October IRGC commander Yadollah Javani said they 'could also be targeted and destroyed' if Iran's infrastructure is hit. Cutting them would not black out India's internet, because traffic reroutes over other cables, but it could slow services to and from West Asia and Europe, and repairs in a war zone could take months.
What is an undersea cable?
It is a fibre-optic line, often no thicker than a garden hose, laid along the seabed to carry data between countries.
When an email goes from Mumbai to London, or a video loads from a server in Europe, the data almost certainly travels as pulses of light through glass fibres inside one of these cables. In the deep ocean a cable is about 17 to 21 mm across. Near the shore, where ships’ anchors and fishing gear are a danger, it is wrapped in armour and grows to 40 to 50 mm.
Satellites carry only a small part of international traffic. They are useful in emergencies but cannot match cables for capacity or speed. Undersea cables carry about 99% of the world’s international internet traffic, which is why the United Nations General Assembly called them “critical communication infrastructure” as long ago as 2010.
Which cables run through Hormuz?
Several systems that tie the Gulf states to India, Europe and Africa.
IRGC officials and the Observer Research Foundation, a Delhi think tank, count seven significant systems crossing the strait. The International Cable Protection Committee, an industry body, counts five active segments. Named systems include FALCON, Gulf Bridge International, SeaMeWe-6 and Asia-Africa-Europe-1, which links Southeast Asia, India, the Gulf, Egypt and southern Europe. Bharti Airtel and Reliance Jio hold stakes in several of them.
Taken together, these cables carry less than 1% of global international bandwidth. Their importance lies less in volume than in geography: they serve the economies of the UAE, Qatar, Saudi Arabia and Oman, and carry traffic between India, West Asia and Europe.
What exactly has Iran threatened?
Destruction, if its own infrastructure is attacked. On Wednesday Brigadier General Yadollah Javani, a senior Revolutionary Guards commander, told the Arabic channel Al-Alam that “the United States and its allies have substantial investments” and that the cables in the strait “could also be targeted and destroyed”.
The threat has been building for months. In April an IRGC-linked news agency published a map of the Gulf’s undersea cables and cloud data centres. In May the military spokesperson Ebrahim Zolfaghari wrote on X: “We will impose fees on internet cables.” Iranian media floated licence fees for cables in waters Iran controls, demanded that Google, Microsoft, Meta and Amazon operate under Iranian law, and sought a monopoly on repairs, citing Egypt’s fees for the Suez Canal as a precedent.
How exposed is India?
More than the global numbers suggest. India’s international traffic lands at a small number of places. TRAI counted 17 international cables coming ashore at 14 cable landing stations in 2023, most of them in Mumbai and Chennai. Traffic bound for Europe and West Asia has to leave through a handful of westward routes, and the Gulf is one of them.
The Observer Research Foundation estimates that about 60% of India’s westward data traffic passes through the Hormuz corridor and that four of the seven cables there matter directly to India. It cites an estimate that a day-long disruption could cost India’s IT and services economy up to $920 million.
What would a cut actually do?
Slow things down, rather than switch them off. Internet traffic reroutes automatically when a cable fails. But the other routes then carry extra load, so users can expect slower speeds, buffering, choppy video calls and lag on cloud services hosted in West Asia or Europe. Trading systems and companies that depend on fast links to Gulf or European data centres would feel it most.
There is a recent example. In early 2024, three cables in the Red Sea were severed by the dragging anchor of a ship that had been hit by Houthi militants, disrupting about a quarter of the traffic on the route between Asia and Europe. One of those cables took five months to repair, because cable ships could not safely enter the conflict zone.
Why are repairs so slow?
Because there are few repair ships, and none of India’s own. A repair ship has to find the break, haul the cable up from the seabed and splice it. TRAI noted in 2023 that India has no domestic marine repair provider: the two main providers serving India are based in Singapore and Dubai, and their ships take 10 to 12 days to arrive. In a war zone, insurers and crews may refuse to go at all.
TRAI recommended that the government back an Indian-flagged repair ship, set up cable depots on both coasts and treat landing stations as critical information infrastructure.
Is anything being done to reduce the risk?
New routes are being built that avoid the Gulf. At the AI Impact Summit in India this year, Google announced a $15 billion subsea project, America-India Connect, with links from India to Singapore, South Africa and Australia that bypass Hormuz. Such cables take years to lay. For now, the safety of India’s westward internet depends partly on whether the confrontation in the Gulf stays away from the seabed.