Israeli spies have been using telephones – and their technological successors – for decades to track down, monitor and even assassinate their enemies.

As early as 1972, as part of their revenge on the Palestine Liberation Organization for the murder of eleven Israeli athletes at the Munich Olympics, Mossad agents replaced the marble base of the telephone used by Mahmoud Hamshari, the PLO representative in Paris, in his French apartment.

As he answered the phone on December 8, an Israeli team nearby remotely detonated the explosives in the replica base. Hamshari lost a leg and later died.

In 1996, Israel’s domestic intelligence agency Shin Bet managed to trick Yahya Ayyash, a skilled Hamas bomb maker responsible for killing dozens of Israelis, into answering a call from his father using a Motorola Alpha cell phone that a Palestinian collaborator had brought to Gaza.

Hidden inside the phone were about 50 grams of explosives – enough to kill anyone who held the phone to their ear. Both incidents are now part of the Israeli spy story.

Among former intelligence officers, these cases are considered textbook examples of success because the phones served several important purposes: they were used to monitor and observe the target before the assassination, to identify and confirm his identity during the assassination, and finally to enable the use of small explosive devices that in both cases killed only Ayyash and Hamshari.

When hundreds of pagers suddenly exploded across Lebanon on Tuesday afternoon, suspicion immediately fell on Israel, the only regional power with a spy network capable of carrying out such a brazen, sophisticated and coordinated attack.

Hezbollah, the militant group whose bombs were detonated in the attack, said: “We hold the Israeli enemy fully responsible.”

The Israeli military declined to comment on the attack, but Prime Minister Benjamin Netanyahu met with his top security officials on Tuesday evening following the explosions that killed at least eight people, including a child, and injured more than 2,700.

The Lebanese militant group had resorted to the pagers to evade Israeli surveillance after Hezbollah leader Hassan Nasrallah publicly urged his members to put away their smartphones as Israel stepped up attacks on Hezbollah commanders amid escalating clashes that have been going on for nearly a year.

Since pagers have neither GPS functions nor microphones or cameras and only allow very limited text transmission, they have – at least in theory – a smaller “attack surface” than smartphones and are therefore more difficult to hack.

Hezbollah appears to prefer these systems because of their simplicity: they collect very little data that could be intercepted by Israeli military intelligence.

But they apparently did not consider the possibility that the tiny devices, which are usually powered by single AA or AAA batteries – the latest models are lithium batteries – could explode.

Many of the explosions were recorded by surveillance cameras while the victims went about their daily lives in supermarkets or walking through southern Beirut.

They appeared to occur half an hour apart and were preceded by either a message or a warning tone, prompting many to pull out their old-fashioned communication devices and look at their LCD screens, according to local media reports and videos posted on social media.

Two former Israeli officials, both experienced in hacking communications systems and other operations by the country’s enemies, told the FT that pager batteries are generally not large enough to explode with sufficient intensity to cause the injuries seen in videos released from Beirut hospitals.

Many of the injured in the videos are missing fingers and have facial injuries, while others are bleeding heavily from their thighs – near normal trouser pockets – and in some cases from their abdomens.

Both former officials said there was not enough publicly available evidence to confirm exactly how the detonations were carried out and coordinated.

They said there were two obvious possibilities: a cyberattack in which malware caused the pager’s lithium battery to overheat and then explode, or an intrusion known as a “supply chain attack” in which a shipment of pagers bound for Lebanon was intercepted and a tiny amount of explosives secretly smuggled into it.

Given the small size of the explosions, both ex-officials said a cyberattack was likely, albeit technically complex.

“It’s not easy, but you can do it remotely with a single device, and even then you can’t be sure if it will catch fire or actually explode,” said one of the former officials. “To do that with hundreds of devices at once? That would be an incredible level of sophistication.”

When Hezbollah abandoned its use of smartphones, acquiring a technology that became largely obsolete in the early 2000s could have required importing large quantities of pagers into Lebanon.

However, it would be relatively easy to integrate them into existing mobile networks, said one of the former Israeli officials.

Even today, there is a small market for pagers in industries where employees need to receive short text messages, from hospitals to restaurants to mail sorting warehouses.

While the text messages themselves could easily be intercepted by Israeli intelligence, their true intent could be obscured by the use of codes or pre-arranged signals, making their appeal to Hezbollah obvious, one of the former officials said.

Since the pagers in Lebanon are most likely members of Hezbollah, attackers can be relatively sure that their main targets are militant, the former official said.

“Even for Hezbollah, this should be a very simple investigation – did all the equipment in question come from the same manufacturer and perhaps arrive in the same or a similar shipment?” one of the former officials said.

“Or was it all sorts of different equipment from all sorts of deliveries distributed to a diverse group (of agents) – young, experienced and political?”

If they all came from a single batch or from a single supplier, there is a possibility that the shipments were intercepted and small amounts of advanced explosives were hidden inside them.

One possibility, said the second official, is that the explosives were hidden in the batteries themselves. Israeli and Western intelligence agencies have long feared that terrorists could try this trick on a commercial aircraft.

For this reason, at many airport security checkpoints, passengers are asked to turn on their laptops to demonstrate that the screen and battery are working and to ensure that the battery compartment has not been replaced with explosives.

The second former official, who was involved in previous Israeli cyber sabotage operations, said it was relatively easy to build a working lithium battery containing a small explosive charge.

However, he said that such a large-scale operation would come with risks: “The enemy is not easy and of course he will carefully examine any device before allowing it near a high-ranking member.”