Stuxnet targets PLCs. They control machinery on factory assembly lines, amusement rides, or centrifuges for separating nuclear material. Stuxnet works by targeting machines using the Microsoft Windows operating system and networks. It then looks for Siemens Step7 software. Stuxnet reportedly compromised Iranian PLCs, collecting information on industrial systems and causing the fast-spinning centrifuges to tear themselves apart. Stuxnet reportedly ruined almost one-fifth of Iran's nuclear centrifuges.