Even before computer security researchers began prying it open, one of the more plausible theories on the origin of the infamous Stuxnet worm claimed that the virus was planted within Iranian nuclear facilities by an Israeli agent using USB memory sticks. A new report from Richard Sale of ISSSource seems to support this theory, citing former and senior US intelligence officials who claim that Israel hired proxies to insure the infection of Iran's Natanz facility.

Since its discovery in 2010, Stuxnet has been billed as the most sophisticated computer virus ever created, a labyrinthine masterwork of code that burrowed into hundreds of thousands of systems using a record-shattering 20 zero-day security exploits. Its programming was so complex that it took researchers months to unravel the virus' true purpose as it lay dormant within computer systems around the world. Further investigation revealed that the virus had a specific list of targets, focusing specifically on SCADA (supervisory control and data acquisition) systems created by Siemens to monitor and control industrial processes. Stuxnet completed its mission after damaging centrifuges used for uranium enrichment in the Natanz facility, as Wired reported last year.

The intelligence officials, who requested anonymity due to their proximity to investigations, believe the agents were recruited from Mujahedeen-e-Khalq (MEK), a group of Iranian dissidents with a sordid and violent history who have been allegedly responsible for targeted killings of Iranian nuclear scientists at the behest of the Israeli intelligence service, Mossad, according to the report. Rather than assume the virus would take root naturally, an agent was reportedly directed to load memory sticks containing the virus code on computer systems deep inside the Natanz facility. According to ISSSource, US officials said they suspect the virus was then unleashed into the systems by the user simply by clicking the executable's icon in Windows.