I've been through a DOD background check and it was done by the FBI. I had to fill out a questionnaire and if I remember correctly they ask you for every address you have lived at for the past 15 years, and every job you have had also. If there are periods of time where you were unemployed, you must supply the name(s) of people who can verify where you were during that time, etc. I think it asked about drug use also. For marijuana, I just put down "experimental use in high school" because I wasn't going to lie.
And then they go talk to everyone you have even smiled at in your life. Okay, not that bad. But they go talk to your neighbors, friends, previous employers. I don't even know how many. I had a lot of calls from people telling me the FBI had been to see them and were asking lots of questions about me.
They went to the PD where I used to dispatch and asked about me. The poor guys there just shook their heads and said, "She's so clean you aren't gonna find anything on her."
I don't believe they talk to you. I don't remember them talking to me.
Depending on who does the investigation, it can take quite a long time. Probably due to their backlog of investigations. It was months before I got my clearance. Some investigations take about 18 months before you get your clearance. Depends on the level of clearance your employer is requesting for you.
But that was not DOJ. Probably DOJ and FBI conduct their investigations differently. Are they doing an actual background check or just the fingerprint check? If you are going into government buildings were there is highly classified work going on, they will be doing a regular background check. I imagine for a Secret clearance level, at minimum. Mostly likely not for Top Secret or for any of the "dark" areas.
Background checks have most likely changed a lot since 9-11. Mine was done sometime in 1980.
Just be sure that you are honest when completing you questionnaire. I still have a copy of mine because it has so much information about me it is a good reference tool.
Best of luck. If you have nothing to hide and have no suspicious backkground stuff going on, it should be no big deal. You probably won't even see the DOJ investigators.
Judy