But a study released Friday by Mr. Chien, Nicolas Falliere and Liam O. Murchu at Symantec, concluded that the program’s real target was to take over frequency converters, a type of power supply that changes its output frequency to control the speed of a motor.

The worm’s code was found to attack converters made by two companies, Fararo Paya in Iran and Vacon in Finland. A separate study conducted by the Department of Homeland Security confirmed that finding, a senior government official said in an interview on Thursday.

Then, on Wednesday, Mr. Albright and a colleague, Andrea Stricker, released a report saying that when the worm ramped up the frequency of the electrical current supplying the centrifuges, they would spin faster and faster. The worm eventually makes the current hit 1,410 Hertz, or cycles per second  just enough, they reported, to send the centrifuges flying apart.

In a spooky flourish, Mr. Albright said in the interview, the worm ends the attack with a command to restore the current to the perfect operating frequency for the centrifuges  which, by that time, would presumably be destroyed.

“It’s striking how close it is to the standard value,” he said.

The computer analysis, his Wednesday report concluded, “makes a legitimate case that Stuxnet could indeed disrupt or destroy” Iranian centrifuge plants.

The latest evidence does not prove Iran was the target, and there have been no confirmed reports of industrial damage linked to Stuxnet. Converters are used to control a number of different machines, including lathes, saws and turbines, and they can be found in gas pipelines and chemical plants. But converters are also essential for nuclear centrifuges.

On Wednesday, the chief of the Department of Homeland Security’s cybersecurity center in Virginia, Sean McGurk, told a Senate committee that the worm was a “game changer” because of the skill with which it was composed and the care with which it was geared toward attacking specific types of equipment.