Stuxnet worm was U.S.-Israel project

The computer worm Stuxnet, that has set back Iran's nuclear program by several months or years, was a joint project between America and Israel, the New York Times reported. Israel tested the virus, designed to destroy Iran's nuclear centrifuges at its Natanz nuclear reactor, at its Dimona complex in the Negev Desert, according to the report published Saturday. Stuxnet reportedly has wiped out about one-fifth of Iran’s nuclear centrifuges, delaying its ability to create its first nuclear weapons. 

According to the newspaper, in 2008 the German company Siemens gave the Idaho National Laboratory information to enable it to identify weaknesses in the computers it sold to Iran for its enrichment facilities.
Those weaknesses are what the Stuxnet worm attacked when it was released the following year.

The worm worked by sending Iran's nuclear centrifuges out of control, while at the same time playing back recordings of normal operations at the nuclear plant, meaning that everything appeared normal to the plant's operators, even as the centrifuges were tearing themselves apart. Neither America nor Israel has admitted to playing a role in designing Stuxnet. In January 2009, The New York Times reported that President Bush authorized a covert program to undermine the electrical and computer systems at the Natanz nuclear plant. President Obama sped up the program, according to the newspaper, citing unnamed officials.