A U.S. cyber-security firm reports that the Stuxnet virus may have first entered Iran's Natanz nuclear facility through computer components that were interdicted and infected by the United States, before being sent on to Iran. According to the report, American intelligence agencies identified the Iranian company NEDA Industrial Group as the primary integrator of Natanz's industrial control system and as Iran's leading expert in Siemens Step7 software. This software is used throughout Iran's nuclear program, including at centrifuge plants. U.S. officials then proceeded to interdict computerized components ordered by NEDA and infected them with the Stuxnet virus. The report was prepared by Critical Intelligence, a U.S. cyber security firm. NEDA was sanctioned by the U.S. Treasury Department in December 2012 for its involvement in the Iranian nuclear program.