These sources, who requested anonymity because of their close proximity to investigations, said a saboteur at the Natanz nuclear facility, probably a member of an Iranian dissident group, used a memory stick to infect the machines there. They said using a person on the ground would greatly increase the probability of computer infection, as opposed to passively waiting for the software to spread through the computer facility. “Iranian double agents” would have helped to target the most vulnerable spots in the system,” one source said. In October 2010, Iran’s intelligence minister, Heydar Moslehi said an unspecified number of “nuclear spies” were arrested in connection with Stuxnet.33 virus.