NEW YORK - Intelligence services of Israel and the United States collaborated in developing a computer virus that reportedly sabotaged Irans nuclear centrifuges and slowed its ability to develop an atomic weapon, The New York Times reported on Sunday. The newspaper reported that Israel has tested the effectiveness of Stuxnet worm at its nuclear facility in Dimona complex in the Negev desert before releasing it. The report quoted intelligence and military experts and officials as saying the effort to create the Stuxnet computer worm was a joint US-Israeli project that also involved collaboration by Britain and Germany. To check out the worm, you have to know the machines, a US expert told the Times. The reason the worm has been effective is that the Israelis tried it out, the expert added. In recent days, the Times pointed out that the retiring chief of Israels Mossad intelligence agency, Meir Dagan, and US Secretary of State Hillary Rodham Clinton separately announced that they believed Irans efforts had been set back by several years. Stuxnet, first identified by Iranian officials in June, is a malware designed to infect computers using German industrial Siemens Supervisory Control and Data Acquisition (SCADA) - a control system favoured by industries that manage water supplies, oil rigs, and power plants. Israel used centrifuges identical to those in Iran to test out the virus that caused setbacks to Tehrans nuclear program, the newspaper said. Israel has spun nuclear centrifuges virtually identical to Irans at Natanz, where Iranian scientists are struggling to enrich uranium, the Times quoted experts saying. Dimona tested the effectiveness of the Stuxnet computer worm, a destructive programme that appears to have wiped out roughly a fifth of Irans nuclear centrifuges and helped delay, though not destroy, Tehrans ability to make its first nuclear arms, the report said. The report alleges Stuxnet was developed by the United States and Israel with the help of Germany and Britain, who may not have been aware of the part they played. The newspaper reported two years ago the German company Siemens cooperated with the American company Idaho National Laboratory, allowing it to identify problems in computer controllers used by Iranian nuclear plants. The following year they were used in Stuxnet, the Times said. Former US President George W. Bush reportedly authorized the programme in January 2009 and President Barack Barack Obama ordered it accelerated with Israels encouragement, the report claims. The report revealed how the virus works. It would secretly record the daily routine at the nuclear plant and play back the recording of a regular day to operators at the plant. This way it would seem that the facility was operating correctly, while the centrifuges were being destroyed. The Stuxnet virus enters computers through removable drives or through the Internet. It then spreads to other computers and any drives that may be plugged into them. The virus searches for computers with Step 7, software that programmes Siemens controllers. After a control is infected, Stuxnet hides itself. After a few days, the virus speeds and slows motors in such a way that could damage them. At the same time, it sends out the false signals described above.