According to the Wall Street Journal Tuesday reports, the US military computers have been hacked by cyberspies, who have supposedly copied data that could adversely affect the use of US fighter jets - the information hacked being related to Pentagon's $300 billion Joint Strike Fighter project.

The Journal reports also say that, some time back, hackers had breached Air Force's air-traffic-control system.

The report adds that with the cyberspies successfully cracking into the Pentagon's costliest weapons program, and taking several terabytes of information about the project's design and electronics systems, it would become easier for America's enemies to defend against the F-35 Lightning I fighter jet.

While most of the extremely 'sensitive' information has not been compromised since it is stored on computers not attached to the Internet, it is still not clear the breach was executed. However, Chinese networks seemingly had a hand in the proceedings, in which vulnerabilities in networks of the contractors were explored.

In the opinion of Aamir Lakhani, security solutions engineer with St. Louis-based system provider World Wide Technology, the breach could have been avoided. He said: "I think one of the ways this could have been prevented is by limiting what kind of information is stored on non-controlled computers. Taking advantage of cloud computing or centralized data themes could help prevent this information from leaking."