Stuxnet is a family of cleverly written malware worms that primarily target SCADA (Supervisory Control and Data Acquistition) control systems for large infrastructures such as industrial power plants. The original Stuxnet worm was first discovered in 2010, and numerous variants of Stuxnet have been identified since then, with most targeting organizations in the country of Iran.
Stuxnet initially spreads via infected removable drives, particularly USB flash drives, before utilizing additional methods to infect other computers on private networks. The original Stuxnet worm was designed to exploit four zero-day attack vulnerabilities in Microsoft Windows operating systems.
Some computer security experts believe that an attack as sophisticated as Stuxnet could have only been conducted with "nation-state support," although there haven’t been any confirmations to date as to which country or countries might have been involved in developing Stuxnet.