“For one, agents had an informant, an academic named Stefan A. Halper, meet with Mr. Page and Mr. Papadopoulos while they were affiliated with the campaign.”
“The F.B.I. did have an undercover agent who posed as Mr. Halper’s assistant during a London meeting with Mr. Papadopoulos in August 2016.”
“Mr. Halper focused on eliciting information from Mr. Page and Mr. Papadopoulos about their ties to Russia.
Mr. Barr has suggested that the F.B.I. assigned other informants as well to figure out whether any Trump associates were working with the Russians.”
https://www.nytimes.com/2019/11/27/u...r-general.html