Today he lives in the San Francisco Bay Area with his wife, Linda, and his two dogs. He self-published his book last week.

Following is an edited transcript of the interview.

IDG News Service: By some estimates there are 15 to 20 of these secret wiretapping rooms across the country. You're the only AT&T employee who has come forward and talked about them in detail. Why?

Mark Klein: Fear. First of all it was a scary time. It still is a scary time, but during the Bush years it was sort of a witch hunt atmosphere and people were afraid. People are afraid of losing their jobs, and it's a rule of thumb that if you become a whistleblower you'll probably lose your job. And if you have a security clearance, you not only lose your job, but you probably will be prosecuted by the government. The Bush administration made that very clear in statements they made over and over again: 'Anybody who reveals anything about our secret programs will be prosecuted and we are running investigations to find out who leaked this to the New York Times.' Well that puts a fear in people.

IDG: Have you heard from other AT&T employees who told you that they knew of these activities?