Iran has been forced to disconnect key oil facilities after suffering a malware attack on Sunday, say reports.
The computer virus is believed to have hit the internal computer systems at Iran's oil ministry and its national oil company.
Equipment on the Kharg island and at other Iranian oil plants has been disconnected from the net as a precaution.
Oil production had not been affected by the attack, said the Mehr news agency.
However, the attack is believed to have been responsible for knocking offline the websites of the Iranian oil ministry and national oil company.
The Ministry website was back in action on Monday but the oil company site has remained unreachable.
An Iranian oil ministry spokesperson was quoted as saying that data about users of the sites had been stolen as a result of the attack. Core data about Iran's oil industry remained safe because it was on computer systems that remain separate from the net, they added.
The terminal on Kharg Island handles about 90% of Iran's oil exports.
Iran is reported to have mobilised a "cyber crisis committee" to handle the aftermath of the attack and bolster defences.
This committee was set up following attacks in 2010 by a virus known as Stuxnet that was aimed at the nation's nuclear programme.