On June 23, 2013, Edward Snowden got on a plane from Hong Kong to Moscow.

He reportedly spent the next 39 days in the Sheremetyevo International Airport, where he formally asked Russia for asylum on July 12 before being whisked away to an undisclosed location on Aug. 1.

Snowden's supporters say the 30-year-old would be free to leave Russia if he received U.S. amnesty or asylum elsewhere, but an expert of Russia's post-Soviet security services (FSB) thinks that is increasingly unlikely.

Besides the low likelihood that another country would accept Snowden, or that the U.S. government would give him amnesty, there is the question of whether his FSB protectors would be willing to let him out with any insights he might have gathered about how the Kremlin treats its special guests.

"Just think of these paranoid guys — they're quite paranoid in most cases," Andrei Soldatov, a Russian investigative journalist who co-wrote a book on the FSB, told Business Insider. "They might think, 'OK, we worked with [Snowden] for many months and if he leaves the country he will not be under our control. And the problem is that now he might start leaking things not about the NSA but the FSB, and how we treated him here.' That might be quite a natural thought for the FSB."

Soldatov does not buy the argument that Snowden must be a spy or that he even knew what would happen from the outset — just that the former NSA systems administrator is in way over his head.

A screenshot of Rossia 24 TV channel shows Edward Snowden on a boat trip in Moscow in September. AP "Remember, Snowden is not a trained intelligence agent," Soldatov told Business Insider. "He does not have the training to deal with this kind of situation."

Soldatov explained that security services do things in steps, and he detailed how the FSB would likely want to have handled Snowden after he reached out to Moscow in Hong Kong.

"The first step is to get Snowden to Moscow," Soldatov said. "The next step is to have him locked for 40 days [to decide what to do] … The next step is to provide him asylum ... Then to say, 'Someone is looking for you, you are in danger.' … And then you have the guy in a controlled environment, and then you can work with him."

Consequently, Soldatov believes that "Snowden made a great mistake when he decided to go to Moscow."

No one outside of the Kremlin really knows where Snowden has been for the past nine months. All the while, the former CIA technician has been surrounded by masters of human exploitation.

In these circumstances, Snowden has probably come to know things that could burn the FSB, just as the former NSA contractor knows things that could burn America's spy services.

"He is protected by the FSB and he might start talking about that protection," Soldatov said. "Maybe the FSB thinks now, or thought some months ago, that they would be happy with him, but I think that in some course of time they would not be happy that Snowden might disclose these things about the secret locations or maybe just about how they treat him."