The data included e-mail addresses associated with every destroyer and amphibious assault ship in the U.S. Navy.
'There is going to be vulnerabilities,' said a Marine colonel. 'It's just how we address those vulnerabilities, how do we go hunt those bad actors and address them.'
The strategy, which Defense Secretary Ash Carter announced during a speech at Stanford University, is part of a concerted effort to be more transparent about the United States' use of tools to defend and deter attacks.
The Pentagon's "national mission" cyber teams have begun monitoring servers used by "high value" adversaries.