Person Has Trashed My Name In My Previous Position As A Dod Contractor And Told Other Companies To Not Hire Me.

I will try to keep this as short as I can. In 2023 I worked in a IT Compliance position as a DOD Contractor on a nearby military base. I was terminated from there after asking some questions about funds being misallocated and misappropriated (It was my job to ask questions like that). I reported this to my supervisor and this person told me "we dont ask questions like that" even though it was in my job description.

I still got unemployment benefits but I found out recently that one of the reasons why I had a difficult time getting a job as a DOD Contractor on the base again was because someone had trashed my name not only in the office but in the building where several other companies worked. I received more than a few emails documenting what this person has done. This person has claimed situations and events that did not even happen, and quite frankly border on the bizarre and makes me question this person's mental state. This person has talked to these other companies and told them to not hire me and I have been made aware it did cost me at least one potential offer.

I know I will need a lawyer on this but what type of lawyer should I be looking for? What other steps should I take.