Breach(2007)

Eric O'Neill, a computer specialist who wants to be made an agent is assigned to clerk for Robert Hanssen, a senior agent with 25 years in the FBI, and to write down everything Hanssen does. O'Neill's told it's an investigation of Hanssen's sexual habits, however Hanssen is really suspected of spying for the Soviet Union and Russia for years and being responsible for the deaths of agents working for the United States.