John Bumgarner, a cyber warfare expert who is chief technology officer of the U.S. Cyber Consequences Unit, holds a notebook computer while posing for a portrait in Charlotte. A cyber warfare expert claims he has linked the Stuxnet computer virus that attacked Iran's nuclear program in 2010 to Conficker, a mysterious worm that surfaced in late 2008 and infected millions of PCs. Conficker was used to open back doors into computers in Iran, then infect them with Stuxnet, according to research Bumgarner, a retired U.S. Army special-operations veteran and former intelligence officer. - Reuters photo

TEHRAN: Iran's oil ministry has come under a “cyber attack,” with its website and affiliated sites appearing to be offline, Iranian media reported on Monday.

The Mehr news agency reported that the websites, including that of the National Iranian Oil Company (NIOC), were targeted from Sunday.

An oil ministry spokesman, Alireza Nikzad, told the Fars news agency the attack was a “virus” which “attempted to delete data on oil ministry servers.”

The ISNA news agency, identifying the virus as “Viper”, said the attack had deleted data off the servers. The ministry spokesman, however, said “essential data” was unharmed.

“The cyber attack has not harmed essential data of the oil ministry and the NIOC because the main servers are not connected to public servers,” Nikzad said, adding that data was available on off-line servers.

He did not give further details.

The Internet websites of the oil ministry (www.mop.ir) and the NIOC (www.nioc.ir) appeared to be inaccessible on Monday.

Iran in 2010 was the target of a massive cyber attack by a highly sophisticated worm called Stuxnet that penetrated at least 30,000 computers across the country and seemed to specifically target machines linked to centrifuges carrying out uranium enrichment.

Many international experts believe the virus was developed by the United States, possibly with Israeli collaboration, to disrupt Iran's disputed nuclear programme.