The latest research from security firm Symantec seems to indicate that the Stuxnet worm was designed to sabotage Iran's uranium enrichment program, rather than disrupt operations at a nuclear power plant as first suspected.
In a blog post, Symnatec Security Response technical director Eric Chien revealed that the highly sophisticated and potentially state sponsored attack actually targets specific systems with a frequency converter drive.
Now this piece of kit is a power supply that can change the frequency of the output and therefore control the speed of a motor. And more interestingly, they can only be found in programmable logic controllers from two specific vendors, one headquartered in Finland and the other in Tehran.
"Stuxnet requires the frequency converter drives to be operating at very high speeds, between 807 Hz and 1210 Hz," Chien wrote.
"While frequency converter drives are used in many industrial control applications, these speeds are used only in a limited number of applications."
Uranium enrichment is one such application, fuelling the theory that Stuxnet was targeted at Iran's Natanz uranium enrichment facility rather than a nuclear power plant, which uses already enriched uranium and doesn't have frequency converter drives on its PLCs.
"In addition to other parameters, over a period of months, Stuxnet changes the output frequency for short periods of time to 1410Hz and then to 2Hz and then to 1064Hz," continued Chien.
"Modification of the output frequency essentially sabotages the automation system from operating properly."
This story is set to run and run, but the details that are emerging emphatically confirm that Stuxnet represents a step change in the way malware can be used.
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