According to the Wall Street Journal, Iran has hacked US oil, gas and power companies. The hackers were able to gain access to control-system software "that could allow them to manipulate oil or gas pipelines". Basically, the hackers are far enough inside that people are starting to get worried.
US officials say that these break ins from Iranian hackers are like reconnaissance missions for Iran. They're gathering information on the operations of energy companies and figuring out how to "disrupt or destroy them in the future". Gaining access to the control-system is serious. The WSJ explains:
Control systems run the operations of critical infrastructure, regulating the flow of oil and gas or electricity, turning systems on and off, and controlling key functions.
In theory, manipulating the software could be used to delete important data or turn off key safety features such as the automatic lubrication of a generator, experts said.
Iran was also accused of launching DDoS attacks on US banks, so this isn't their first time jumping into cyber warfare (of course, the US and Israel launched the Stuxnet virus on Iran first). For what it's worth, Iran denies involvement with the hackings, but hey, that's what China says about hacking us too. The next World War is so going to start because of some hacker. [WSJ]