The mass pager attack against Hezbollah in Lebanon has turned the spotlight on Israel's secretive Unit 8200, the Israel Defense Forces' intelligence unit, which a Western security source said was involved in planning the operation.

Israeli officials have remained silent on the audacious intelligence operation that killed 12 people on Tuesday and wounded thousands of Hezbollah operatives. At least one person was killed on Wednesday when hand-held radios used by Hezbollah detonated.

A senior Lebanese security source and another source told Reuters that Israel's Mossad spy agency was responsible for a sophisticated operation to plant a small quantity of explosives inside 5,000 pagers ordered by Hezbollah.

One Western security source told Reuters that Unit 8200, a military unit that is not part of the spy agency, was involved in the development stage of the operation against Hezbollah, which was over a year in the making.

The source said Unit 8200 was involved in the technical side of testing how they could insert explosive material within the manufacturing process.

The Israeli military declined to comment. The prime minister's office that has oversight of Mossad did not immediately respond to a request for comment.

Yossi Kuperwasser, a former military intelligence official and now research director at the Israel Defense and Security Forum, said there was no confirmation that the military intelligence unit was involved in the attack.

But he said 8200's members were some of the best and brightest personnel in the Israeli military, serving in a unit at the centre of Israel's defence capabilities.

"The challenges they are facing are immense, very demanding, and we need the best people to get involved in that," he said.

The unit - and its legion of young, hand-picked soldiers - develops and operates intelligence gathering tools and is often likened to the U.S. National Security Agency.

In a rare public statement about the unit's activities, the IDF said in 2018 that it had helped to thwart an air attack by Islamic State on a Western country. At the time, it said the unit's operations ran from intelligence gathering and cyber defence to "technological attacks and strikes."

While Israel has never confirmed its involvement, Unit 8200 was reported to have been involved in the Stuxnet attack that disabled Iranian nuclear centrifuges as well as a series of other high profile operations outside Israel.

Young recruits

The unit is effectively Israel's early warning system, and like much of the rest of the defence and security establishment, shouldered some of the blame for failing to detect Hamas' Oct. 7 assault on southern Israel.

Its commander last week said he was stepping down. In his resignation letter carried by Israeli media, he said he hadn't fulfilled his mission.

The unit is famous for a work culture that emphasizes out-of-the-box thinking to tackle issues previously not encountered or imagined. This helped some graduates build Israel's high-tech sector and some of its biggest companies.

"Whether it's a problem with software weakness, math, encryption, a problem hacking into something ... you must be capable to do it on your own," said Avi Shua, a graduate of 8200, who went on to co-found Orca Security, a cloud security unicorn.

The unit has a high turnover rate of young recruits replacing veterans, said Kobi Samboursky, another former 8200 member and Managing Partner at Glilot Capital Partners, an early stage fund investing in cybersecurity and artificial intelligence.

"The most significant thing here is the 'can-do' culture, where everything is possible," Samboursky said.