The attack crippled computers used to control rocket and missile launches.
The United States launched cyber attacks against Iranian missile control systems and a spy network this week after Tehran downed an American surveillance drone, US media reported on Saturday.
US President Donald Trump ordered a retaliatory military strike against Iran after the drone shootdown but then called it off, saying the response wouldn't be "proportionate" and instead pledged new sanctions on the country.
But after the drone's downing, Trump secretly authorized US Cyber Command to carry out a retaliatory cyber attack on Iran, The Washington Post reported.
The attack crippled computers used to control rocket and missile launches, according to the Post, which cited people familiar with the matter.
Yahoo cited two former intelligence officials as saying the US targeted a spying group responsible for tracking ships in the strategic Strait of Hormuz, where Washington has blamed Iran for two recent mine attacks on oil tankers.
The Post said the strikes, which caused no casualties, had been planned for weeks and were first proposed as a response to the tanker attacks.
US defense officials refused to confirm the reports.
"As a matter of policy and for operational security, we do not discuss cyberspace operations, intelligence or planning," Defense Department spokeswoman Heather Babb told AFP.
On a day trip scheduled after Iran shot down a US drone, Pompeo flew into the Red Sea city of Jeddah and met with King Salman at his palace.
President Donald Trump has blamed Iran for attacks on oil tankers near the strategic Strait of Hormuz, but he also held out hope that implicit US threats to use force will yield talks with the Islamic Republic as the Pentagon
US President Donald Trump approved military strikes on Friday against Iran in retaliation for the downing of an unmanned $130-million surveillance drone, but pulled back from launching the attacks, the New York Times said.
In a statement on Saturday, the Ministry of Foreign Affairs and International Cooperation reiterated its assertion that a political solution is the only way to end the conflict in Libya under the supervision of the United Nations.
President His Highness Sheikh Khalifa Bin Zayed Al Nahyan has sent a message of condolences to Sultan of Brunei Haji Hassanal Bolkiah Mu’Izzaddin Waddaulah on the death of his son Prince Haji 'Abdul 'Azim.
The World Health Organization (WHO) has donated 8.8 tonnes of medical supplies to Syria to aid the country's fight against the Covid-19 pandemic, state media reported.