Exactly how the bureau is working with tech firms remains unclear.
Prosecutors reportedly weighed exposing intelligence vs. the likelihood of punishing IRA backers in the United States.
Yevgeniy Nikulin was in regular contact with Oleksandr Ieremenko, a Ukrainian national who allegedly hacked the U.S. Securities and Exchange Commission.
The fight between law enforcement and tech companies over encryption is about to enter another round.
The suit alleges he violated his non-disclosure agreements with both the NSA and CIA by publishing his memoir.
The news comes weeks after the Justice Department made public charges against another 80 people accused of similar crimes.