Yuri Kozlov is an agent with the CIA.
He will be, as the first recorded adventure proceeds, though there will be a good number of those working at Langley who are extremely skeptical about his motives or purpose. As we are told in the blurb for that introduction, Kozlov is known the intelligence agencies of the West as the "Russian James Bond" and as such as much a part of that country's secret service system as anyone else so why he would decide to go over to the other side was the open question.
This trilogy is said to be "a three-part journey into the political unrest that forces Russia's most famous spy to choose between his legacy and who he wants to become."