The damage to two submarine cables off Perth has revived concerns over one of the world’s least visible vulnerabilities: the infrastructure carrying international internet and communications traffic.
Australia’s Indigo West and Indigo Central cables suffered faults last weekend inside the Submarine Cable Protection Zone off Perth.
Subco chief executive Bevan Slattery said the faults occurred “straight after each other and in close proximity” and pointed to “very suspicious activity from a vessel near the location”. The Australian Federal Police is assessing a report relating to the incident, said ABC News.
There is no public evidence yet that the cables were deliberately damaged. Ships’ anchors and fishing activity routinely cause cable failures.
But a vessel’s movements have attracted attention. Maritime intelligence company Windward said its analysis of AIS data and satellite imagery identified one vessel whose movements matched the location and timing of the faults.
The vessel entered Australia’s exclusive economic zone on July 28 and remained off Perth for almost two weeks. Windward said its AIS track showed repeated crossings of the cable corridor around August 8 and 9, when the damage occurred. S
atellite imagery provided another layer: electro-optical imagery placed the vessel about 11 kilometres west of Perth on August 3, while synthetic aperture radar imagery on August 8 placed it over the cable route.
The concern is not confined to Australia.
Newsweek recently reported that a Chinese research vessel had been observed operating over undersea cables connecting the United States with Taiwan and the Philippines.
According to the report, Windward had tracked the 200-foot China-flagged vessel “loitering at slow speed” directly over the Pacific Light Cable Network in the Philippine Sea, an approximately 8,000-mile trans-Pacific fibre-optic system.
Windward said the ship had also operated repeatedly around the disputed Paracel and Spratly islands, as well as in the Bay of Bengal and off Sri Lanka.
Taken together, the Perth and Pacific cases illustrate why vessel tracking has become important to cable security.
A ship does not need to be caught cutting a cable for its movements to raise questions. Repeated loitering or unusual manoeuvring over a cable route can provide investigators with a lead that can then be tested against satellite imagery, ship records and physical evidence from the damaged cable.
Europe has already faced similar questions.
In November 2024, two telecommunications cables in the Baltic Sea were damaged within hours of each other. A Chinese-flagged cargo ship, Yi Peng 3 , was operating in the vicinity and became the focus of an investigation. A month later, Finland seized the tanker Eagle S after the Estlink 2 power cable and several telecommunications cables were damaged, reported Reuters.
But not every suspicious case has turned out to be sabotage. Swedish authorities concluded that the cargo ship Vezhen had damaged a cable between Sweden and Latvia in January 2025, but ruled out deliberate action, saying the vessel’s anchor had caused the damage.
About 16 submarine cables carry the bulk of Australia’s international communications. That leaves the country dependent on a relatively small number of physical routes that run for thousands of kilometres across the seabed, notes ABC.
Its international connectivity depends on cables landing at a limited number of coastal locations, while those cables pass through long maritime routes linking India with Southeast Asia, West Asia, Africa and Europe.
A cable does not have to be cut near Mumbai or Chennai to affect Indian connectivity. Damage elsewhere can force traffic onto alternative routes, reducing capacity or increasing latency.
The Red Sea has already demonstrated this exposure. Cable damage in the region disrupted international routes serving India and other parts of Asia, showing that India’s communications security depends not only on its landing stations but on the safety of the maritime routes leading to them.
The problem is therefore twofold: where cables come ashore and what happens to them at sea. It also makes attribution critical. AIS data can show where a vessel reported itself to be. Satellite imagery can establish its presence. Neither establishes intent. Physical examination of the cable, anchor damage, vessel records and other evidence are needed to determine what actually happened.
China has rejected the broader suggestion that Chinese maritime activity around submarine cables should be treated as evidence of hostile intent.
Responding to Australian concerns, the state-run Global Times accused Canberra of “over-securitization” and cited Chinese officials and academics arguing that there was insufficient evidence to blame China for cable incidents. It also noted that cables are routinely damaged by normal maritime activity.
That argument cannot simply be dismissed. The Baltic cases demonstrate why: some incidents remain unresolved, while others initially regarded as suspicious were eventually judged accidental.
But the Perth incident shows why governments are increasingly treating submarine cables as critical infrastructure rather than simply telecommunications equipment.
The immediate question is what damaged Indigo West and Indigo Central. The larger question is whether Australia, India and other cable-dependent countries can detect unusual activity, identify the vessels involved and establish what happened before an isolated cable failure becomes a wider communications crisis.
The internet may be wireless at the user end. But its international backbone is still sitting on the seabed.
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