The US launched a secret cyber attack against Iran following the September attacks on Saudi Arabia’s oil facilities.
Two US officials have told the Reuters news agency that the operation took place in late September and was aimed at stopping Tehran from spreading “propaganda.”
One of the officials said the strike affected physical hardware, but did not provide further details.
The operation also follows the downing of an American drone in June and an alleged attack by Iran’s Revolutionary Guards on oil tankers in the Gulf in May.
Saudi Arabia, Britain, France, the United States and Germany have blamed the September attack on Iran.
Tehran has denied any involvement, although the Iran-aligned Houthi militant group in Yemen have claimed responsibility.
The Pentagon has responded by sending thousands of extra troops and equipment to boost Saudi defences.
The Pentagon declined to comment about the cyber strike, with spokeswoman Elissa Smith saying: “As a matter of policy and for operational security, we do not discuss cyberspace operations, intelligence, or planning,”
It is not known what the impact the attack has had. James Lewis, a cyber expert with the Washington-based Center for Strategic and International Studies, said: “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.”
Tensions in the Gulf have escalated since May 2018 when Mr Trump withdrew from a 2015 deal between global powers and Tehran which put limits on Iran’s nuclear programme in exchange for the easing of sanctions.
Iran has also carried out cyber attacks against the US – this month, a hacking group that appears to be linked to the Iranian government tried to infiltrate email accounts related to the president’s re-election campaign.
Over a 30-day period in August and September, the group, which Microsoft dubbed “Phosphorous,” made more than 2,700 attempts to identify consumer accounts and attacked 241 of them.
Tensions with Iran have been high since the bombing of Saudi oil facilities, with Tehran claiming that an Iranian tanker was hit by rockets in the Red Sea last week and warning on Monday that there would be consequences.
President Hassan Rouhani has ruled out bilateral talks with the US unless Washington returns to the nuclear deal and lifts crippling economic sanctions.