Hezbollah pagers: How did they explode and who is responsible?

Analysts have been quick to express shock at the scale of Tuesday’s attack – saying Hezbollah prides itself on its security measures.

Some suggested a hack may have caused the pager batteries to overheat, causing the devices to explode. Such an act would be unprecedented.

But many experts say that is unlikely, with footage of the explosions inconsistent with the batteries overheating.

Some analysts say instead that some sort of supply chain attack, which involved the pagers being tampered with during their manufacture or in transit, was more likely.

Supply chain attacks are a growing concern in the cyber security world with many high-profile incidents recently caused by hackers gaining access to products whilst they are in development.

But these attacks are normally contained to software. Hardware supply chain attacks are far rarer as they involve getting hands on to the device.

If this was indeed a supply chain attack it would have involved a huge operation to secretly tamper with the pagers in some way.

A former British Army munitions expert, who asked not to be named, told the BBC the devices could have been packed with between 10 to 20 grams each of military-grade high explosive, hidden inside a fake electronic component.

This, said the expert, would have been armed by a signal, something called an alphanumeric text message.