A frontpagemag.com post by Rich Trzupek may provide the best description of havoc wreaked by computer worm. Stuxnet, introduced most likely by flash drive, hopped computers at Iran's uranium enrichment facility at Natanz until it reached its target. The computer worm then went to work by targeting the programmable logic controller (PLC) that controls thousands of centrifuges at the facility.
The PLC fooled centrifuges into changing speeds, and at the same time, not reporting the change or triggering alarms. "Operators were surely puzzled, for their control panels told them everything was running normally, but centrifuge after centrifuge was being wrecked by the severe changes in rotation speed. The result, many experts believe, is that thousands of the centrifuges were damaged over the course of the year..." It's widely believed only a rich nation could provide the resources for a computer worm of Stuxnet's sophistication. Ralph Langner, a computer security expert,compares it to the "arrival of a F-35 into a WWI battlefield". The scary thought is: now that the code is public, where will it turn up next?