An Italian nuclear engineer and his sister have been arrested by police on charges of conducting a massive cyber-espionage operation that hacked into the emails of two former prime ministers, Vatican cardinals and Mario Draghi, the president of the European Central Bank.

Giulio Occhionero, 45, and his sister Francesca Maria Occhionero, 48, who have residency in the UK but are believed to have been most recently living in Italy, were arrested on charges of stealing state secrets and illegal hacking.

Mr Occhionero, who investigators said had strong links to the Masonic movement, allegedly developed software that infected email accounts, enabling him to access the information.

He called the “malware” or computer virus “Eye Pyramid” – an apparent reference to the all-seeing eye of God, or Eye of Providence, a symbol often associated with Freemasonry that appears on the US one dollar bill. The name of the software may also have been a play on his own surname – Occhionero means “black eye” in Italian.