Charges are set to be announced against four defendants, including two Russian security services officers, over a massive data breach at internet giant Yahoo.
A US official said two of the defendants are Russian FSB officers and the other two are criminal hackers.
One of the defendants has been taken into custody in Canada.
The US justice department is expected to publicly announce the charges later on Wednesday.
The charges arise from a 2014 compromise of Yahoo user accounts and would be the first case brought against Russian government officials.