Iran temporarily shut down centrifuges: IAEA

TEHRAN: The International Atomic Energy Agency, the U.N. nuclear watchdog, reported Tuesday that on Nov. 16, Iran stopping feeding hot uranium gas into its thousands of centrifuges, and that the shutdown could have lasted as long as seven days.

The disclosure came after intense speculation that a computer worm known as Stuxnet had been manufactured specifically to target the centrifuge machines at the Natanz facility, which Iran says is used to produce fuel for electricity and which the United States suspects is part of a weapons program.

The IAEA report was tantalizing, experts said, but inconclusive, especially because it also indicated that Iran has in recent months brought more than 1,000 new centrifuges on line. The kind of centrifuge used is prone to shutdowns and malfunctions.

Still, a number of researchers have determined that the Stuxnet worm was designed to make the type of centrifuge - a Pakistani copy of an old Dutch design - spin wildly out of control.

"The shutdown is definitely interesting," said Ivanka Barzashka, research associate at the Federation of American Scientists. "It is consistent with replacing all of the software operating your controls." She said that the increasing evidence that Stuxnet was aimed at the type of centrifuge Iran primarily uses is "too much of a coincidence, in my opinion."

Israel and the United States are seen as the most likely sources for the cyberwarfare suggested by Stuxnet - officials in both countries have declined to comment - but Iran has denied that it was harmed by Stuxnet or that it is facing serious technical problems with its uranium-enrichment program.

Iranian Vice President Ali Akbar Salehi, who is also the head of the Iranian Atomic Energy Organization, acknowledged Tuesday that Iran was the subject of a computer attack, but he placed it far in the past.

"One year and several months ago, Westerners sent a virus to [our] country's nuclear sites," he said, according to a news agency.