Iranian hackers gained access to control-system software that could allow them to manipulate oil or gas pipelines. Malware found in the power grid that could be used to deliver malicious software to damage plants. Targets have included several American oil, gas and electricity companies, which government officials have refused to identify. Iran has denied being the source of any attacks, adding that it had been a victim of American sabotage. Mandiant announced that the Chinese government was backing the attacks. However, officials from the government in Beijing vehemently denied any connection.
Source: https://thehackernews.com/2013/05/iranian-hackers-targeting-us-oil-gas.html