Stuxnet virus that hit Iranian nuclear program in 2010 according a new research proposed by Symantec security company. Researchers have found in the code of earlier version of St.uxnet a version reference 0.5. The attacker strategy was to destroy the nuclear plant causing an explosion due the sabotage of gas valves, hackers purpose was physical destruction of the targets. Later versions significantly increased their spreading capability exploiting an increased number of vulnerabilities, but has described before the most important change is related to the strategy pursued by the attackers moved their attention from gas valve disruption to centrifuge speed modification.
Source: https://thehackernews.com/2013/02/stuxnet-05-symantec-study-reveals_27.html