According to the New York Times the attack was code-named Nitro Zeus and would have crippled Iran’s air defences, communications systems and key parts of its electrical power grid.
It was put on hold after a nuclear deal was reached last year.
The plan was set up by the Pentagon to give President Barack Obama that he had alternatives to war if Iran moved against the United States or its regional allies. It involved thousands of US military and intelligence personnel and would have required tens of millions of dollars and putting electronic devices in Iran’s computer networks.
US intelligence agencies at the same time developed a separate plan for a covert cyberattack to disable Iran’s Fordo nuclear enrichment site inside a mountain near the city of Qom.