Snowden: US and Israel did create Stuxnet attack code
NSA whistleblower Edward Snowden has confirmed that the Stuxnet malware used to attack Iranian nuclear facilities was created as part of a joint operation between the Israelis and the NSA's Foreign Affairs Directorate (FAD).
The Stuxnet code, which has been deployed since 2005, is thought to be the first malware aimed specifically at damaging specific physical infrastructure*, and was inserted into the computer networks of the Iranian nuclear fuel factory in Natanz shortly after it opened.
Early variants attempted to contaminate uranium supplies by interfering with the flow of gas to the fuel being processed, potentially causing explosive results in the processing factory. Later a more advanced variant attacked the centrifuges themselves, burning out motors by rapidly starting and stopping the units and contaminating fuel production, although it may actually have encouraged the Iranians.