The new Strategy for Operating in Cyberspace, issued by the US Department of Defense on Thursday, covers a collection of topics that have been discussed for years and leaves a number of important unanswered questions, critics said.

Deputy Secretary of Defense William Lynn unveiled the new strategy during a speech, a transcript of which is available online.

"Our strategy's overriding emphasis is on denying the benefit of an attack. Rather than rely on the threat of retaliation alone to deter attacks in cyberspace, we aim to change our adversaries' incentives in a more fundamental way. If an attack will not have its intended effect, those who wish us harm will have less reason to target us through cyberspace in the first place," Lynn said.

The plan contains a handful of initiatives, including treating cyberspace as a domain like land and sea, introducing new network defences that include sensors, software and signatures to detect and stop malicious code, coordinating with the Department of Homeland Security and the private sector and working with other countries.

"Some of these things have been written about for years," said Rich Mogull, an analyst at Securosis. "The real challenge is, are they going to actually execute this?"

For example, the document stresses the need to work closely with private companies, to secure those providing key services such as electricity and those that serve government agencies. "It's one thing to talk about public-private partnerships, that's in every document going back 15 years," Mogull said. "But it's another to actually work out those partnerships."

He sees some indications that the DoD may finally be getting serious about cyberdefence, however. For example, the strategy stipulates that speeding up the DoD's information technology acquisition process is critical. "DoD's acquisition processes and regulations must match the technology development lifecycle. With information technology, this means cycles of 12 to 36 months, not seven or eight years," according to the policy.

Mogull hasn't heard much in the past about the agency trying to speed up technology acquisition. "Traditionally, that's been a big problem," Mogull said, noting that the DoD's massive size has historically meant it has moved very slowly.

Also, recent attacks have probably served as enough of a wake-up call that the government realises it has to take cybersecurity seriously, he said. While there have been attacks for years, there have been a few notable ones in the past year or two, he said.

In his speech, Lynn revealed that in March, 24,000 files were stolen in a single intrusion at a defence company. He did not reveal more details about the breach but said that generally speaking, while some data that gets stolen is mundane, some involves sensitive systems such as aircraft avionics, surveillance technologies and satellite communications.

The policy is a good first start, said Congressman Jim Langevin. But he pointed out a few issues that still need answers.

For example, he'd like to know what are the acceptable "red lines" that justify action in cyberspace. He wonders whether data theft can trigger warfare or if the US would have to wait for a physical event, such as an attack on the country's power grid, before responding militarily.

In May, the DoD said that all options, including physical attacks, are possible in response to a cyber attack.