A "secret legal review" on the use of US cyberweapons has concluded that President Barack Obama can order a pre-emptive cyber strike against countries if it is required to protect the country’s computer networks, according to a report by the New York Times.

The new policy will also stipulate how the intelligence agencies carry out searches on foreign computer networks to find potential threats on the US, and upon the President’s approval, attack rivals.

US military officers have also supported the principle of first strike if there is evidence of an imminent large scale digital attack against the country’s cyber networks.

Additionally, the US Department of Defense (DoD) is also planning to add more troops and civilians, as part of its move to counter threats against government computer networks.

The move comes after a warning from the US defence secretary, Leon Panetta, who revealed that the nation could witness a ‘cyber-Pearl Harbor’.

As per the new policies, the US DoD would not be involved in defending ordinary cyberattacks on US firms or individuals – the Department of Homeland Security would be responsible for that; while investigations of cyberattacks or theft would be handled by the Federal Bureau of Investigation (FBI).

According to reports, Obama is known to have ordered the deployment of cyberweapons only once, when he authorised an increasing series of cyberattacks over Iran’s nuclear enrichment facilities.