Stuxnet was designed to modify motors used in industrial processes, according to security company Symantec.
The malware attacks specific motors used in processes like uranium enrichment, said Symantec.
"Stuxnet monitors the current operating frequency of these motors, which must be between 807Hz and 1,210Hz, before Stuxnet modifies their behaviour," said Symantec researcher Eric Chien in a blog post on Friday.
Specifically, the piece of malware modifies programmable logic controllers (PLCs) in industrial-control-system frequency converter drives used to control the motors, for the purposes of sabotage. Stuxnet only attacks the frequency converter drives from two vendors — one Finnish, one Iranian, said Chien.
"Over a period of months, Stuxnet changes the output frequency [of the motors] for short periods of time to 1,410Hz and then to 2Hz and then to 1,064Hz," said the Symantec researcher. "Modification of the output frequency essentially sabotages the automation system from operating properly."
Chien said that Symantec had modified its research paper on Stuxnet (PDF).