NORAD, which monitors the skies 'round the clock for terrorist and nuclear threats, faces ongoing security problems after moving out of Cheyenne Mountain and into the basement of an office building on Peterson Air Force base in Colorado Springs last year. That's what I found in my reporting for an investigation in today's Washington Times, citing an internal document that recommends "difficult and costly retrofits and new construction to correct numerous physical vulnerabilities" to the North American Aerospace Defense Command. The problem, according to the document, is that the building was "not designed to house" NORAD, which remains vulnerable to an aerial strike or truck bomb. It wasn't always this way: NORAD used to be secure inside the mountain but relocated amid many unanswered questions, according toÂ this investigation I did with the Times' national security writer, Bill Gertz. David Hill also wrote about these changes for a former edition of 5280. Air Force officials say they are addressing problems.