"When you look at encrypted communications, if they are properly encrypted, there is no real way to tell that they are encrypted. You can't distinguish a properly encrypted communication, at least in the theoretical sense, from random noise. So if you have an alien civilization trying to listen for other civilizations, or our civilization trying to listen for aliens, there's only one small period in the development of their society where all of their communications will be sent via the most primitive and most unprotected means," Snowden said.

"When we think about everything we're hearing from our satellites, or everything they're hearing from our civilization, if there are indeed aliens out there, all of their communications are encrypted by default. So what we're hearing — which is actually an alien television show or a phone call or a message between their planet and their own GPS constellation, whatever it happens to be — is indistinguishable to us from cosmic microwave background radiation," he added.

Snowden is currently living in Asylum in Russia, and is wanted in the United States to face charges under the federal Espionage Act.

Earlier this year, we reported that a federal appeals court ruled that the controversial NSA spy program which collects phone records is actually illegal.