The US Department of Defense has been under "systematic" attack from hackers over the past two weeks, a spokesperson said today.
Only limited details were made available but the attacks were said to be widespread and sometimes sophisticated.
The attacks were only on unclassified networks used by the various branches of the US military and achieved some degree of penetration.
"It was the most organised and systematic attack the Pentagon has seen to date," said John Hamre, deputy Secretary of Defense.
Hamre said it was possible the attacks were part of a hackers' competition currently taking place.
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