In the late 1970s, American spy Jim Olson was stationed in Moscow. At the time, it was one of the riskiest and highest-stakes CIA stations in the world.  

Olson, who served more than 30 years overseas, had been intercepting sensitive Russian information that was being sent over microwave transmissions. He knew that, if they were caught, it could mean spending the rest of their lives in a Soviet prison. 

Many of the transmissions dealt with military and defense information, and they eventually discovered their tactic of intercepting these messages was under threat. Something more secure was in the works for the Russians: their communications were going underground.  

"We know exactly what they're doing," Olson told CNBC Senior Washington Correspondent Eamon Javers on the latest episode of CNBC's new original podcast series "The Crimes of Putin's Trader."  

For this series, Eamon Javers spent nearly a year investigating a criminal network and exploring how wealthy Russian hackers stole millions from U.S. investors. Javers interviewed FBI agents, prosecutors — and even spies like Olson — to reveal the shocking details of a massive criminal enterprise. 

In episode six, Javers talks with Olson, who details his dangerous mission to retain a crucial well of information. After satellite images confirmed the Russians had already started digging the tunnels for the cable, the CIA operatives knew they had to do something quickly – before the well ran dry. 

"We decided to go after it," he said. 

Olson and two other operatives were designated for assignment in Moscow and trained on how to tap into those cables (and how to do it covertly).  

But that mission wasn't easy: Olson had to disguise himself as a Russian peasant, taking a public bus out to the countryside on a route often patrolled by militia. He broke into a manhole on the side of a highway, monitored for potential poisonous gas (or Russian police) in the tunnel and lowered himself into the shadows.  

Javers asked Olson what it feels like to go on such a mission, something he called "Mission Impossible stuff." He asked if fear ever entered his mind. 

"Fear doesn't enter into it because you are so mission-focused," Olson said. "We just do what we're trained to do and it's a great sense of accomplishment when you carry something out like that."  

For spies like Olson who put their lives on the line, motivation is everything.  

"It's humbling because you have this sense that your country put that much trust in you to carry out that mission," Olson said. "And that you can make a significant contribution to our country's security – it's pretty heavy stuff."  

Listen to "The Crimes of Putin's Trader" now.