Industrial computers infected by Stuxnet in Iran have been cleaned and returned to their units, a top official said on Sunday, following reports that the malware was mutating and wreaking havoc with equipment.

"The industrial computers infected by the Stuxnet virus have been cleaned," Mohsen Hatam, deputy industry minister, was quoted as saying on the state television's website.

Iranian media had said that Stuxnet had mutated and was wreaking havoc on computerised industrial equipment in Iran, with around 30,000 IP addresses infected.

But Hatam said that "all platforms have been cleaned and delivered to the industrial units."

"The virus infected these computers because they lacked high security firewalls," he added.

He said Stuxnet was "designed and despatched about a year ago to gather information from industrial computers."

Stuxnet, which was publicly identified in June, is a self-replicating malware found lurking on Siemens systems, mostly in India, Indonesia and Pakistan, but the heaviest infiltration appears to be in Iran, researchers say.

Analysts say Stuxnet may have been designed to target Iran's nuclear facilities, especially the Russian-built first atomic power plant in the southern city of Bushehr.

Officials have denied that Bushehr was among the addresses penetrated by the worm, but had acknowledged that some personal computers of the plant's personnel had been infected.

Iran's nuclear ambitions are at the heart of a conflict between Tehran and the West, which suspects the Islamic republic is seeking to develop atomic weapons under the cover of a civilian drive.

Tehran denies the allegation and is pressing on with its uranium enrichment programme -- the most controversial aspect of its nuclear activities -- despite four sets of UN Security Council sanctions.

earlier related report
Holiday concerns in China over 'cyber superweapon'
Hong Kong (AFP) Oct 1, 2010 - Computer hackers have warned that a week-long national holiday in China from Friday could leave the country vulnerable to further attack from a potentially lethal computer virus.

The Stuxnet cyberworm, dubbed the world's "first cyber superweapon" by experts and which may have been designed to attack Iran's nuclear facilities, has already hit millions of computers around the country.

Stuxnet is feared by experts around the globe as it can break into computers that control machinery at the heart of industry, allowing an attacker to assume control of critical systems like pumps, motors, alarms and valves.

It could, technically, make factory boilers explode, destroy gas pipelines or even cause a nuclear plant to malfunction.

China's biggest hacker group told the South China Morning Post on Friday that cybersecurity staffing at large state-owned enterprises would be minimal during the holiday to mark the founding of the People's Republic of China.

"China's industrial networks become incredibly weak and therefore much easier to infiltrate during the national holiday, because everybody is off," a spokesman for the Chinese Honker Union told the paper.

"So if they are up to something they may very likely do it now."

Stuxnet is believed to target control systems made by German industrial giant Siemens commonly used to manage water supplies, oil rigs, power plants and other industrial facilities.

The computer worm -- a piece of malicious software (malware) which copies itself and sends itself on to other computers in a network -- was first spotted by Siemens on July 15, a company spokesman told AFP.

There are also concerns that the holiday could slow any Chinese government response.