A new virus appears to have been state-sponsored, and aimed at Iran:
There was speculation among experts yesterday that the target could have been the Bushehr nuclear reactor in Iran — which was loaded with Russian uranium fuel last month – and that Israeli hackers were behind the sophisticated operation. But security analysts said it may be impossible to identify the perpetrators.

The computer security firm, Symantec, which has been charting Stuxnet's spread, estimates that the group behind it would have been well funded, comprising between five and 10 people, and that it would have taken six months to prepare.
Meanwhile, American cyber-defense is lacking:
Experts say that questions of legal authority in the unique environment of cyberspace -- where the networks critical to government and even military operations are owned and operated by the private sector -- are a problem for U.S. cybersecurity efforts across the government.

Gen. Alexander said the administration is still grappling, as its predecessors had, with the exact role military, civilian and private sector entities would play in cybersecurity.