“The sophistication of the worm, plus the fact that the designer had inside intelligence on the Iranian facility, led Langner to conclude that the United States had developed Stuxnet, possibly with the help of Israeli intelligence.
Langner isn’t shy about naming the U.S. as the Stuxnet culprit, as he stated in a recent speech at the Brookings Institution. In that speech, he also made the bigger point that having developed Stuxnet as a computer weapon, the United States has in effect introduced it into the world’s cyber-arsenal.”
Source: Security Expert: U.S. ‘Leading Force’ Behind Stuxnet : NPR