I was recruited out of college. An interviewer came to my college and had scheduled interviews set up by the college of engineering. The interview took about 30 minutes. After this, I received an invitation for a recruiting weekend in Tucson. They flew me down, rented me a car, and put me in a very nice resort, along with over a hundred other soon-to-be college grads. We got a site tour, a few nice meals, and a morning of interviews with various departments.
Unfortunately, I was not mapped into the correct departments and had to request an interview with the department that ultimately hired me. Each interview was approximately 20 minutes, focusing on the work I had done in college and my area of expertise. Interviews as this level focused on technical expertise rather than obscure psychological questions.
It is important to note that after being hired, there is a lengthy and very in-depth application process for a DOD security clearance. This process goes into your past 5 to 7 years, depending on the level of clearance required. Applicants are required to list places they have lived, as well as individuals they have known and their contact information. It speeds the process considerably to have this information available beforehand.