WILLIAM J. BROAD, JOHN MARKOFF and DAVID E. SANGER - The Dimona complex in the Negev desert is famous as the heavily guarded heart of Israel’s never-acknowledged nuclear arms program, where neat rows of factories make atomic fuel for the arsenal.
Over the past two years, according to intelligence and military experts familiar with its operations, Dimona has taken on a new, equally secret role — as a critical testing ground in a joint American and Israeli effort to undermine Iran’s efforts to make a bomb of its own.
Behind Dimona’s barbed wire, the experts say, Israel has spun nuclear centrifuges virtually identical to Iran’s at Natanz, where Iranian scientists are struggling to enrich uranium. They say Dimona tested the effectiveness of the Stuxnet computer worm, a destructive program that appears to have wiped out roughly a fifth of Iran’s nuclear centrifuges and helped delay, though not destroy, Tehran’s ability to make its first nuclear arms.
“To check out the worm, you have to know the machines,” said an American expert on nuclear intelligence. “The reason the worm has been effective is that the Israelis tried it out.”
Though American and Israeli officials refuse to talk publicly about what goes on at Dimona, the operations there, as well as related efforts in the United States, are among the newest and strongest clues suggesting that the virus was designed as an American-Israeli project to sabotage the Iranian program. ...
the worm only kicked into gear when it detected the presence of a specific configuration of controllers, running a set of processes that appear to exist only in a centrifuge plant. “The attackers took great care to make sure that only their designated targets were hit,” he said. “It was a marksman’s job.”
For example, one small section of the code appears designed to send commands to 984 machines linked together.
Curiously, when international inspectors visited Natanz in late 2009, they found that the Iranians had taken out of service a total of exactly 984 machines that had been running the previous summer.
But as Mr. Langner kept peeling back the layers, he found more — what he calls the “dual warhead.” One part of the program is designed to lie dormant for long periods, then speed up the machines so that the spinning rotors in the centrifuges wobble and then destroy themselves. Another part, called a “man in the middle” in the computer world, sends out those false sensor signals to make the system believe everything is running smoothly. That prevents a safety system from kicking in, which would shut down the plant before it could self-destruct.
“Code analysis makes it clear that Stuxnet is not about sending a message or proving a concept,” Mr. Langner later wrote. “It is about destroying its targets with utmost determination in military style.”
This was not the work of hackers, he quickly concluded. It had to be the work of someone who knew his way around the specific quirks of the Siemens controllers and had an intimate understanding of exactly how the Iranians had designed their enrichment operations. ...
via Stuxnet Worm Used Against Iran Was Tested in Israel - NYTimes.com.