Denise Zheng, a former government cybersecurity specialist and now a senior fellow at the Center for Strategic and International Studies in Washington, said Silicon Valley is home to "the loudest dissenting voices on what our intelligence and national security agencies are doing."

Facebook Visit

Carter's cooperation plea came in a speech at Stanford University, beginning a two-day visit that will also include stops at the headquarters of Facebook Inc. and venture capital firm Andreessen Horowitz.

The defense secretary plans to establish a full-time office in Silicon Valley, staffed with personnel who will scout emerging technologies that the military could use. The Pentagon also plans to set up its own branch of the U.S. Digital Service, which overhauled the flawed healthcare.gov website last year.

His initiative reflects a turnaround for a government institution that once served as a principal incubator of breakthrough technologies, including a forerunner of the Internet.

Today, innovations in microelectronics, global positioning systems and software applications are more likely to emerge from a West Coast office park than from a government lab.

That's why the Pentagon must shift from its traditional role of technology exporter to becoming a technology importer, said a department official who briefed reporters on condition of anonymity in advance of Carter's presentation.

Pentagon Hacked

Obama administration officials have increasingly been sounding the alarm about the risk of cyber-assaults on government and commercial networks.

In the prepared text for his Stanford speech, Carter disclosed that Russian hackers intruded into one of the Pentagon's unclassified computer networks. The penetration was detected and "a crack team of incident responders" began hunting the Russians within 24 hours, Carter said.

The Russians had entered the Defense Department network through "an old vulnerability in one of our legacy networks that hadn't been patched," he added.

'Urgent' Concern

Pentagon cybersecurity personnel evicted the Russian hackers "in a way that minimized their chances of returning," Carter said, calling the episode an example of the department's ability to protect itself.

John Brennan, the director of the Central Intelligence Agency, last month called cyberthreats "an urgent national security priority" and announced formation of a new digital innovation unit.

Pentagon officials said their new strategy grew in part from concern over increasingly severe and sophisticated cyber-attacks. Carter said in his prepared remarks that the approach includes providing "offensive cyber options that, if directed by the president, can augment our other defense systems."

Since the department's previous strategy was released in 2011, institutions from Sony Pictures Entertainment to the White House have been victimized.

Hackers, including from more than 100 foreign intelligence agencies, probe Pentagon computer networks millions of times each day, Eric Rosenbach, Carter's top adviser on cybersecurity, told the Senate Armed Services Committee this month.

"These cyberthreats continue to increase and evolve, posing greater risks to the networks and systems of the Department of Defense our national critical infrastructure and U.S. companies and interests," Rosenbach said.

Approach 'Ineffective'

Baker, now an attorney with Steptoe & Johnson LLP, said efforts to deter attacks are insufficient.

"I've yet to see indications that DoD is writing a cyberstrategy to win," he said. "Instead, we're talking about 'deterring' them, which we've been remarkably ineffective at."

The Pentagon also has struggled to retain cybersecurity specialists in an era when the private sector can offer even relatively junior personnel big paychecks.

The military will have a hard time capitalizing on commercial breakthroughs with "a procurement cycle designed to buy aircraft in the World War II era," said Fred Kagan, a defense specialist at the American Enterprise Institute in Washington.

–With assistance from David Lerman in Washington.