Yuri was a Ukrainian man contacted by weapons dealer Michael Amador at about 11:37pm on Day 3. Amador called him to say that the Cordilla virus would be sold within the hour (to Nina Myers, who was representing an unspecified party). Yuri did not know that Amador merely sold a hidden bomb to Nina and traveled to Los Angeles to sell the actual virus to Stephen Saunders for $10 million of purely personal profit.
Since the virus was created by Ukrainian biologists, it is certain that Yuri was one of the scientists or a representative of them. Yuri believed that the virus was sold in Mexico, and he presumably received part of the funds from Nina's account.