Symantec: All Stuxnet worm attacks were launched by infecting a total of just 10 machines. Virus was designed to sabotage the high-frequency convertor drives used in a uranium enrichment facility in Iran. Researchers found that every infection could be traced back to just one of 10 infected machines. Iran blocked out the worm in August 2010, but the attacks appear to have been successful, researchers say. Researchers: Iran blocked outward connections to the command and control servers, rather than a drop-off in infections.”]
Source: https://www.darkreading.com/attacks-breaches/stuxnet-iran-attack-launched-from-10-machines