Releasing its first-ever comprehensive approach to cyber defence, the Pentagon said that creating common awareness and warning capabilities will enhance collective self-defence against cyber attacks.

The Defence Department will seek increasingly robust international relationships to reflect our core commitments and common interests in cyberspace, the strategy document said.

The Pentagon last year established US Cyber Command, part of an effort to develop an approach to protecting the countrys most sensitive computer networks.

Military officials have acknowledged that cyber attacks could be construed as acts of war, which might justify retaliation. But Thursdays release backed off the notion of using the cyber domain for offensive operations by shifting focus to defending against attacks.

The cyber threats we face are urgent, sometimes uncertain and potentially devastating as adversaries constantly search for vulnerabilities, Deputy Defence Secretary William Lynn said in announcing the strategy.

Just as the Pentagon revealed the strategy, The New York Times, citing senior US officials, reported that the military suffered once of its worst-ever digital attacks in March, when foreign hackers broke into the computer system of a corporate contractor and acquired 24,000 sensitive documents.

The officials did not identify the company or the country of origin, saying that is was a matter of confidential diplomatic discussions, the newspaper said.

China has long been blamed for hacking into US systems. But it was unclear in those cases whether the government was involved or if it was the work of others inside the country. China has flatly rejected accusations of hacking.

Lynn disclosed that over the years the Pentagon has been victimized by hacking. He said crucial files have been stolen from defence industry data networks, including sensitive information about missile tracking, satellite navigation, unmanned aerial vehicles and advanced jet fighters.

A great deal of it concerns our most sensitive systems, including aircraft avionics, surveillance technologies, satellite communications systems and network security protocols, Lynn said.

In releasing the new strategy, the Pentagon said 60,000 new malicious software programmes are identified every day that pose a threat to security, the economy and ordinary citizens.

Strong partnerships with other US government departments and agencies, the private sector and foreign nations are crucial, Lynn said. Our success in cyberspace depends on a robust public-private partnership. The defense of the military will matter little unless our civilian critical infrastructure is also able to withstand attacks.

The Pentagon said it is enhancing its best practices regime to improve cyber security and hygiene. It will also strengthen internal monitoring and communications to guard against insider threats, and is developing new operating concepts and designs to prevent hacking.

The strategy calls for newer technology involving sensors, software and intelligence to detect and stop malicious activities before the Pentagons networks and systems can be accessed.