Washington, Apr. 21 : Computer spies have broken into the Pentagon''s 300 billion dollar Joint Strike Fighter project - the Defense Department''s costliest weapons program ever - according to current and former government officials familiar with the attacks.

According to Fox News, the latest intrusions provide new evidence that a battle is heating up between the U. S. and potential adversaries over the data networks that tie the world together.

The revelations follow a recent Wall Street Journal report that computers used to control the U. S. electrical-distribution system, as well as other infrastructure, have also been infiltrated by spies abroad.

Attacks like these - or U. S. awareness of them - appear to have escalated in the past six months, said one former official briefed on the matter.

Former U. S. officials say the attacks appear to have originated in China. However it can be extremely difficult to determine the true origin because it is easy to mask identities online. (ANI)