In an interview with US TV network NBC, Snowden said: “I was trained as a spy in sort of the traditional sense of the word in that I lived and worked undercover overseas - pretending to work in a job that I’m not - and even being assigned a name that was not mine.”
“I don’t work with people. I don’t recruit agents. What I do is I put systems to work for the United States. And I’ve done that at all levels from - from the bottom on the ground all the way to the top.”
Snowden gave the interview in Moscow, where he is currently in exile after revealing the details of NSA intelligence-gathering programmes to journalists.
Snowden is thought to have obtained more than 1.7 million files relating to NSA monitoring of emails, phone calls and internet browsing.
Snowden was elected Rector of Glasgow University in February. At his inauguration in April, Snowden addressed students via video link.
Snowden said: “In a democracy people have a right to know the policies of their government...this idea that if we believe in something we should stand up for it is what I will follow in my role as Rector of the University.”
There have been calls to offer Snowden asylum in Scotland; he faces charges of theft of government property, unauthorized communication of national defense information and willful communication of classified intelligence to an unauthorized person.