While officials say there is no evidence the hackers acquired any sensitive information, they are concerned about the apparent escalation of targets, The Wall Street Journal reported. They said previous breaches traced to Iran have been aimed at banks and energy companies.
The Journal reported its sources said Defense Secretary Chuck Hagel and Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, were briefed on the intrusion and on the response to it. The Defense Department would not confirm the Iranian intrusion.
"We take these attempts seriously and work to learn lessons from every one of them," a spokesman said.
Officials said the Navy hacking suggests Iran's computer capabilities may be better than U.S. security agencies believed.
The discovery comes at a time when Iranian President Hassan Rouhani has made overtures to President Obama to restart talks on Iran's nuclear program.