Hezbollah has launched a new weapon against northern Israel in its latest round of fighting: tiny drones controlled by fiber-optic cables, the width of dental floss, that evade electronic detection.

These drones – widely used in the Ukraine war – are small, difficult to track and potentially deadly.

Many drones are susceptible to electronic jamming by air defenses. Jamming can cause the drone to crash or return to its original location. But fiber optic drones are not remotely controlled. They have a thin cable that connects the operator directly to the drone, making it impossible to jam electronically.

Drones are not ideal because the wind – or other drones – can cause the cables to become tangled.

But, “if you know what you’re doing, it’s absolutely lethal,” said Robert Tollist, a drone expert and researcher at the Royal United Services Institute in London, about how a drone can fly low and crawl over a target.

Experts say troops must either intercept the drones, which is difficult due to their small size and short flight path, or find a way to cut the nearly invisible cable.

Hezbollah – an Iranian-backed militant group in Lebanon – has mostly used fiber-optic drones on Israeli troops operating in southern Lebanon or border towns.

An Israeli military official told the AP that Hezbollah appears to have turned to new types of drones because Israeli air defenses have been successful against larger and more powerful rockets, missiles and other drones. He was speaking on condition of anonymity as per military guidelines.

He said Israel believes drones are locally made and easy to build — requiring an off-the-shelf drone, a small amount of explosives, and transparent wire that is readily available on the consumer market.

He described drones as the biggest threat to troops inside Lebanon, but said the Israeli military was working on a technical solution. Meanwhile, Israel is taking measures on the ground to protect soldiers, such as adding nets and cages to military vehicles.