WASHINGTON (Reuters) - The unclassified email network at the U.S. military's Joint Staff has been offline since late July after what investigators now believe was a sophisticated cyber attack likely linked to a foreign state, U.S. officials said on Thursday.
The officials, who spoke to Reuters on condition of anonymity, did not say what country was to blame.
NBC cited unnamed officials attributing the intrusion to Russia, saying however it was unclear whether it was the work of Russian government or individuals.
The Pentagon declined comment. It first acknowledged on July 28 that the unclassified networks of the U.S. military's Joint Staff was taken offline after suspicious activity.
(Reporting by Phil Stewart; Editing by Sandra Maler)