In the US, all persons or companies paid by foreign sources to further the interests of those foreign sources are required to register with the US Justice Department. They file their papers quarterly. It allows the public and Congress to know who is trying to influence whom.
U.S. says working on initiative to de-escalate Syria fighting, with focus on Aleppo (Reuters)
from the article: Leftists denounce new bill on NGO funding as 'McCarthyist'