Experts generally believe a small mount of stable explosive was carefully implanted into each sabotaged device. Alan Woodward, a professor of cybersecurity at Surrey University, said: “There wouldn’t need to be much explosive, as proximity to a human body means it would cause injury even if it was a few grams.”

The first wave of explosions – which occurred from about 3.30pm local time on Tuesday – appear to have been triggered by a special message from Hezbollah leadership, implying, Woodward argued, a specific modification of the pagers’ embedded software. This meant it would trigger an explosion when the appropriate message was sent.

It may have been a default setting on the pagers, but the trigger message came with a cynical twist. Eyewitnesses say the pager bleeped, then paused, then detonated – giving enough time for them to be brought closer to the owner’s face – which is why Lebanese doctors reported treating multiple hand and eye injuries after the blast. Source