I know everyone believes they fully understand that foreign aid is a free grab bag for graft, but at least for the portion that is military aid (a very large slice), that is simply not true. I also do not believe it is true of State Department managed funds, but of that I do not have personal experience. I'll again point out that I was, as a Major General, the Chief of US Army Security Assistance (I am sorry if noting my experience again triggers the easily offended). In other words, I oversaw negotiation, award, and management of all US Army international security assistance programs. As I have pointed out repeatedly, a large measure of US military assistance is in kind. Combat platforms that we are no longer using. Two exceptions are Egypt and Israel which benefit from appropriations resulting from the peace accords following the Yom Kippur War.
In those cases and others, I also managed new military assistance programs where an authorization and appropriation was then competed for a procurement for the assisted nation. No money changes hands. The appropriation was handled just like any other procurement by the Army except the end item and accompanying maintenance and training packages went to the foreign source. There is no pile of lose cash to access.
I obviously worked very closely with my two counterparts in the Air Force and Navy. Each service has very strict auditing procedures, and then each service is further audited by DOD.
The strictness of US program management has historically meant that allies would buy or participate in the most critical programs with the US - for instance M1 Abrams, Bradley, and Paladin for Saudi Arabia - and less critical materiel from other countries with less strict accounting - Saudi Arabia's European truck fleet. The shared development and procurement of the F-16 and now F-35 are Air Force examples.
It is curious to me that so many feel compelled to believe there is some kickback scheme involved in international assistance.
What one does find internationally are bribery schemes where a foreign company bribes a foreign procurement decision maker to win a contract. Large American defense corporations watch for that very carefully, and any individual caught doing so is personally criminally liable. But that is rather different than the nonsense that American officials are somehow skimming millions from foreign aid.