An internal confidential document from the United Nations, leaked to The New Humanitarian and seen by The Associated Press, says that dozens of servers were "compromised" at offices in Geneva and Vienna.
Those include the U.N. human rights office, which has often been a lightning rod of criticism from autocratic governments for its calling-out of rights abuses.
One U.N. official told the AP that the hack, which was first detected over the summer, appeared "sophisticated" and that the extent of the damage remains unclear, especially in terms of personal, secret or compromising information that may have been stolen. The official, who spoke only on condition of anonymity to speak freely about the episode, said systems have since been reinforced.
The level of sophistication was so high that it was possible a state-backed actor might have been behind it, the official said.
There were conflicting accounts about the significance of the incursion.