PORTLAND — Combining mechanical and combat systems into an integrated network aboard U.S. warships presents cybersecurity challenges, but there’s no evidence that a Navy ship has ever been hacked, according to one of the Navy’s top cybersecurity officials.

The stealthy Zumwalt that’s under construction at Maine’s Bath Iron Works represents the highest level of automation and integration to date on a destroyer, Rear Adm. William Leigher said.

“The real key for Zumwalt is doing the exhaustive testing that we will do as the ship starts to come to life and doing the training that we need to as we understand the nuances of the ship,” said Leigher, the Navy’s director of Warfare Integration for Information Dominance.

Leigher, a native of Appleton, returned to his home state to deliver a keynote address Friday at a University of Southern Maine conference bringing together information technology officers to talk about cybersecurity, cyber ethics and resources for small businesses.

The USM graduate said the first Navy ship he served aboard was powered by a steam engine and was controlled by valves that had to be turned by hand.

The Navy’s current destroyers are light years beyond that and the Zumwalt takes it to another level, with so much automation that the crew size will be nearly halved.

In his job, working for the chief of naval operations, Leigher is responsible for overseeing the Navy’s future programs for network systems, intelligence, shipboard systems, unmanned aircraft and weapon systems.

Cybersecurity and network operations are a big part of the 200 programs — including some systems aboard the Zumwalt — that fall under his purview.

His biggest concerns, he said, are about 450,000 computers used by the Navy, threats from nation states and groups like Anonymous that try to penetrate networks, and networked systems that are integrated aboard Navy warships and submarines operating around the world.

“Anyone who turns on a computer is introducing some threat at various levels,” he said. “The sheer size of the Navy’s network is a problem for us.”

In commercial ships, a private security firm has demonstrated the ability to hack a system Automatic Identification System used by thousands of ships around the world, either disengaging the system or altering it to send out erroneous data or to create phantom vessels.

But the Navy doesn’t believe anyone has managed to hack a system aboard a U.S. warship, and Leigher wants to make sure that no one does.

“Our security is very good, but if I thought it was perfect, then I could go home at 3 o’clock after every day, and I don’t,” he said. “It takes all of our attention to sharpen the skills of our operators and to make sure we have the most relevant technology.”