Also in 2008, Siemens asked the Department of Homeland Security to conduct a security assessment on its popular PCS 7 control systems, a fact highlighted in a conference hosted by the IHL and Siemens that year in Chicago.
Stuxnet targeted Siemens' PCS 7 control systems and its Step 7 software.
Israel, meanwhile, set up an unknown number of gas centrifuges at its top-secret Dimona complex, then tested Stuxnet on the machines and their control systems, according to the New York Times. The centrifuges were virtually identical to the ones used by Iran.
Dubbed "P-1" centrifuges because they were Pakistan's first-generation design, the machines are notoriously unpredictable, and often fail at rates much higher than more sophisticated designs. Iran's centrifuges are knock-offs of the P-1, and are usually identified as "IR-1" models.
But the Israelis, and perhaps the Americans at their own Oak Ridge National Laboratory in Tennessee, succeeded in getting several P-1 centrifuges up and running, the New York Times said. The publication cited an anonymous American expert in nuclear intelligence, who told the paper that the Israelis had used the P-1 centrifuges at Dimona to test Stuxnet's effectiveness.
An Israeli link to Stuxnet has been long suspected, both because Israel has been vocal about the danger posed by a nuclear-armed Iran and because of several obscure clues buried in the worm's code. Rather than launch a military strike, as it did against an unfinished Iraqi nuclear reactor in 1981, the scenario goes, the country decided to wage cyber warfare.
Other hints came from security researchers, who unanimously agreed that Stuxnet's complexity pointed to a state-sponsored project, probably one that involved a large team of programmers, SCADA experts and intelligence analysts.
Langner, who has spent months pulling the worm apart, said earlier this week that Stuxnet was a natural weapon for opponents of Iran's nuclear program to unsheathe.
"If any target would justify a full-blown cyberwar strike for the first time in history, those centrifuges certainly would," Langner said Jan. 10 on his blog , where he has spelled out his findings and speculations. Langner believes that Stuxnet's creators had access to what he called a "mockup test system" to try out their worm on actual centrifuges.
Although Stuxnet has apparently not crippled Iran's nuclear program, it seems to have seriously hindered it, perhaps more than some have thought. Just last week, for example, the outgoing head of Israel's Mossad intelligence service said setbacks meant Iran wouldn't be able to create a bomb before 2015.