Kaspersky said he had been tipped off about the leak by a technician at the Russian plant.
"[T]heir nuclear plant network which was disconnected from the internet ... was badly infected by Stuxnet," Kaspersky was quoted as saying by Australia's SC Magazine.
Kaspersky also told his audience that the malware was later transported by Russian astronauts to the space station on a USB stick.
The sophisticated Stuxnet worm was estimated to have set Iran’s nuclear program back by two years, after it was discovered in June 2010 to have attacked computers at the Islamic Republic's plant in Natanz.
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