So when does sex become a security problem?

In fact, during the Cold War, the KGB (and allied services, including the East German Stasi under Markus Wolf, and Cuban intelligence) frequently sought to entrap CIA officers.

CIA officers in Russia were strongly warned about “swallows,” the term for the beautiful women the KGB deployed to try to seduce Americans, which was a constant danger at Moscow station.

One former CIA officer said that while sexual entrapment wasn't generally a good tool to recruit a foreign official, it was sometimes employed successfully to solve short-term problems. For example, this officer was once stationed in a Middle Eastern country and wanted to shut down a known spy from a neighboring state who was also posted there. To make a long story short, the CIA obtained video footage of the man in intimate embrace with his local girlfriend. When the man turned down a recruiting pitch, the agency mailed the images to his wife.