Stuxnet multiplies

You've heard of Stuxnet --the destructive computer virus unleashed on Iran's nuclear facilities. It was believed to be the world's first cyber weapon. But now we're learning that it has a twin --and the twin actually came first and started eating away at Iran's nuclear facility at Natanz years before the more public version we learned about in 2010. The bad news for Iran's nuclear programmers is that it's not really clear how broad the Stuxnet family is.