The U.S. carried out the cyber operations with the objective of undermining Iran's capabilities to spread "propaganda", two U.S. officials told Reuters on the condition of anonymity.
"As a matter of policy and for operational security, we do not discuss cyberspace operations, intelligence, or planning", said Pentagon spokeswoman Elissa Smith.
An incident involving Iran's Sabiti oil tanker on October 11 in the Red Sea increasingly appears to have resulted from an attack, marking the latest major hostile incident in a region on edge in recent months after Iranian or Iranian-backed attacks on oil-related targets.
On September 14, the Abqaiq facility and the Khurais oil field in Saudi Arabia were hit by attacks, which resulted in the temporary suspension of 5.7 million bpd of Saudi Arabia's crude oil production, or around 5 percent of global daily oil supply.
The impact of the attack, if any, could take months to determine, but cyber strikes are seen as a less-provocative option below the threshold of war.
"You can do damage without killing people or blowing things up; it adds an option to the toolkit that we didn't have before and our willingness to use it is important", James Lewis, a cyber expert with the Washington-based Center for Strategic and International Studies, told Reuters.
Lewis added that it may not be possible to deter Iranian behavior with even conventional military strikes.
It was unclear whether there have been other USA cyber attacks since the one in late September. The group made more than 2,700 attempts to identify these accounts, then attacked 241 of them.
The ISI DG, who in the last week of September quietly visited Iran and Saudi Arabia, is believed to have played a major role in laying the ground for de-escalation in the Middle East. Officials said he would be the focal person for future contacts between Saudi Arabia and Iran.
At the end of last week, Iran said that explosions hit one of its oil tankers off the Saudi port city of Jeddah in the Red Sea, damaging the vessel and causing an oil spill. Iranian officials claimed same day that the tanker was stable, not leaking oil and returning to Iran.
According to Reuters, more than 70 websites are stealthily pushing Iranian propaganda in 15 countries.
Tensions between Iran and U.S. have soared since Donald Trump pulled out of a 2015 nuclear deal.