Researchers at security firm Symantec have revealed that the Stuxnet was targeted at five different organisations operating in Iran.
As the nuclear sites are unlikely to be connected directly to the Internet, attacks could have been instigated by infecting industrial organizations sharing information and malware with plants such as Natanz.
In a blog post, the company said that it evaluated a total of 3,280 unique samples of the Stuxnet attacks that contained 12,000 infections, only a fraction of all the known infections.
Symantec also revealed that three of the five organisations were attacked once, one was targeted twice while another was attacked three times.
The organisations, all of which have a presence in Iran, were targeted in June 2009, July 2009, March 2010, April 2010 and May 2010.
“We have a total of 3,280 unique samples representing approximately 12,000 infections. While this is only a percentage of all known infections, we were able to learn some interesting aspects of how Stuxnet spread and where it was targeted,” the company said in a statement.