Three U.S. officials told the Associated Press that the operation on Thursday evening disabled Iranian computer systems that controlled Iran’s rocket and missile launchers.
The officials spoke on condition of anonymity because they were not authorized to speak publicly. Yahoo News first reported the cyber strike.
Two of the officials say President Donald Trump authorised the cyber strike even as he called off a conventional military response to Iran’s downing of a U.S. surveillance drone.
The officials say defense officials had prepared such a cyber response as a contingency plan for weeks preceding the attack.
Cybersecurity firms say Iran has increased its offensive cyberattacks against the U.S. government and critical infrastructure as tensions have grown between the two nations.
CrowdStrike and FireEye, which regularly track such activity, say in recent weeks hackers believed to be working for the Iranian government have targeted U.S. government agencies, as well as sectors of the economy, including oil and gas.
The firms say the hackers have sent waves of spear-phishing emails.
It is not known if the hackers managed to gain access to the targeted networks with the emails, which typically mimic legitimate emails but contain malicious software.
The cyber offensive is the latest chapter in ongoing cyber operations between the U.S. and Iran. The recent sharp increase is occurring after the Trump administration imposed sanctions on the Iranian petrochemical sector this month.