Cyber spies linked to China have accessed the private emails and email address books of "many" top Obama administration officials, according to a senior U.S. intelligence official and a top secret document obtained by NBC News.
The intrusion, first codenamed "Dancing Panda" then "Legion Amethyst," was detected in April 2010, according to a top secret NSA briefing from 2014.
Government email accounts assigned to the officials, which are more secure, were not hacked.
The names of the government officials whose emails were accessed were not disclosed.
The time period overlaps with Hillary Clinton's use of a private email account while secretary of state.
A senior official told NBC News the intrusion into personal emails in ongoing.