Hezbollah has launched a new weapon against northern Israel in the latest round of fighting: small drones controlled with fiber-optic cables the width of dental floss that avoid electronic detection.

These drones — used widely in the war in Ukraine — are small, hard to track and potentially lethal.

Many drones are susceptible to electronic jamming by air defenses. Jamming can cause a drone to crash or return to its point of origin.

But fiber-optic drones are not controlled remotely. They have a thin cable that connects an operator directly to the drone, making it impossible to electronically jam.

The drones are not infallible because the wind — or other drones — can cause the cables to tangle.

But, “if you know what you’re doing, it’s absolutely deadly,” said Robert Tollast, a drone expert and researcher at the Royal United Services Institute in London , explaining how the drone can fly low and creep up on a target.

Experts say militaries must either intercept the drones, which is difficult due to…