Stuxnet

Stuxnet is a malicious computer worm discovered in 2010, believed to have been in development since at least 2005. It targets supervisory control and data acquisition (SCADA) systems and is thought to have caused significant damage to Iran's nuclear program. Stuxnet is believed to be a cyberweapon built jointly by the US and Israel, exploiting four zero-day flaws to target machines using Microsoft Windows and Siemens Step7 software. The worm compromised Iranian PLCs, collecting information and causing centrifuges to malfunction, and infected over 200,000 computers worldwide. Stuxnet has three modules: a worm, a link file, and a rootkit component, and is typically introduced to the target environment via an infected USB flash drive.learn more on wikipedia