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A device can eavesdrop on someone talking near a fibre-optic cable, even if there is a large distance between them

Fibre-optic cables use light to transmit data Russell Kord/Alamy

Fibre-optic cables use light to transmit data

Fibre-optic cables, such as those used in internet infrastructure, could be used for eavesdropping. A device that can pick up tiny changes in signals sent through the cables can detect words spoken from over a kilometre away.

Optical fibres use beams of light to transport data across the world, underground and in the oceans. Researchers have previously found that these cables can also be used as sensors – for example, to detect earthquakes and track whales. Now, Bo Wang at Tsinghua University in …

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