Robert M. Lee, chief executive of Dragos Inc., which specializes in industrial control system security, said Iranian hackers have been very aggressive in trying to gain access to utilities, factories, and oil and gas facilities. That doesn’t mean they’ve succeeded, however. In one case in 2013 where they did break into the control system of a U.S. dam — garnering significant media attention — Lee said they probably didn't know the compromised target was a small flood control structure 20 miles north of New York City.