Stuxnet has hit worker computers at Iran's first nuclear power plant, although attacks have been successfully fended off so far, it has emerged.
The virus is thought to be the first to directly target major infrastructure complexes and is used to control functions at industrial plants and utilities facilities.
Until now, however, the worm was not known to have hit any major sites in Iran.
Project manager at the Bushehr nuclear plant, Mahmoud Jafari, told the official IRNA news agency in Iran a team was currently trying to take the malware out of a number of computers, the Associated Press reported.
So far, Stuxnet "has not caused any damage to major systems of the plant," Jafari said, and the facility is still set to go online next month as planned.
Two of these security holes have not yet been patched, although Microsoft said it hopes to issue fixes in an upcoming security bulletin.
Graham Titterington, principal Ovum analyst, said he expected to see more Stuxnet attacks soon.
"Although the criminal hacker community is well organised and well resourced, it is unlikely that they would have invested so much effort in this one attack, which appears to be more politically than economically motivated," Titterington said.
"Nation level attacks on IT systems have occurred in Georgia, Estonia and in several Middle East countries in the last few years, and so it is not surprising if something similar is happening in this case."
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Tom Brewster is currently an associate editor at Forbes and an award-winning journalist who covers cyber security, surveillance, and privacy. Starting his career at ITPro as a staff writer and working up to a senior staff writer role, Tom has been covering the tech industry for more than ten years and is considered one of the leading journalists in his specialism.
He is a proud alum of the University of Sheffield where he secured an undergraduate degree in English Literature before undertaking a certification from General Assembly in web development.