There is nothing you could do except to wait but I won't put too much hope on it. To give you general ideal of how the process works, see below.
1-A. Apply for positon(s) on Northrop Grumman website.
1-B. If everything looks good on resume then, Northrop will contact you to schedule for interview (I think it was few weeks).
2. During the interview, they ask typical questions, like what is your strength/weakness? Tell me about yourself? etc....
3. If the interview went well then they will contact you within 72 hours by either phone or email, in my case it was email.
4. They will disclose salary and other information to you.
5. Accept or decline job offer.
Conclusion is that if you don't hear from Northrop within a month, chances are you didnt get it. I recommend you continue to applying for other positions even if one of them is in "Hiring Manager Review" phase. This phase doesn't guarantee that you will have an interview.
*side note*. I declined the job offer due to personal reasons so I lack the ability to help you.