Russia’s effort to undermine the 2016 U.S. election shows that covert operations are as much a danger now as they were at the height of the Cold War. The staff writer David Grann moderated a panel at the 2013 New Yorker Festival that included Tony Mendez, the former C.I.A. agent whose exploits in Iran inspired the movie “Argo”; Jeff Moss, who founded the hacker conference DEFCON and now advises the Department of Homeland Security; Stella Rimington, a former director of the British intelligence agency M.I.5; and Joe Weisberg, the former C.I.A. officer who created the TV show “The Americans.” They debate the value of human intelligence versus surveillance, the differences between American and British intelligence, the ethics of assassination and drones, and whether espionage sometimes does more harm than good.