Office of the Inspector General looks at this stuff.
Trump fired 17 of them:
https://campaignlegal.org/update/significance-firing-inspect...
> This blatantly illegal and incredibly concerning mass firing removes the only independent offices within agencies designed to protect taxpayer money and root out corruption, fraud, waste and mismanagement.
I also posted the 2022 report the office generated elsewhere in the thread, a follow up to their 2015 report.