Nuclear inspectors working in Iran found the country’s enrichment programme at the Natanz enrichment plant temporarily shut last week, the International Atomic Energy Agency reported earlier this week. IIran’s P-1 centrifuges were developed from a 1970s European design and have been prone to breakdowns. A rapid expansion of enrichment in 2007-08 exacerbated the problems. An IAEA report in September 2010 said the number of producing centrifuges had fallen to 3,772 from 3,936 a few months earlier. Delays in Iran’s enrichment campaign could buy more time for efforts to find a diplomatic solution to its stand-off with the world powers over the nature of its nuclear activities.

The Stuxnet computer virus may be one of the factors causing the shutdown. Stuxnet, a malicious computer worm that attacks command modules for industrial equipment, has been described as a first-of-its-kind guided cyber missile. Stuxnet was discovered in July 2010, but is likely to have existed for at least a one year before that. The majority of infections have been found in Iran.

Rumours abound concerning the source of the virus: there is speculation that it is an attempt by a hostile state to sabotage Iran’s nuclear activities, gas pipelines or power plant. The ultimate goal of Stuxnet is to sabotage facilities by reprogramming programmable logic controllers (PLCs) to operate out of their specified boundaries in a way that the attackers specify.

International computer safety and security experts Symantec say that Stuxnet looks for industrial control systems and then changes the code in them to allow the attackers to take control of these systems without the operators knowing. “In other words, this threat is designed to allow hackers to manipulate real-world equipment, which makes it very dangerous.”

The Symantec dossier on Stuxnet published earlier this month says, “It is the first computer virus to be able to wreak havoc in the physical world. It is sophisticated, well-funded, and there are not many groups that could pull this kind of threat off. It is also the first cyberattack we’ve seen specifically targeting industrial control systems.”

The worm is made up of complex computer code that requires many different skills to put it together. Symantec security experts estimate it took five to ten people to work on this project for six months. In addition, knowledge of industrial control systems was needed along with access to such systems to do quality assurance testing; again indicating that this was a highly organized and well-funded project.