Mostly Russian originals
A classified KGB training manual on “confidential contacts” explores the gray area between informant and agent.
In addition to its espionage abroad, the KGB was always busy recruiting foreign nationals in the Soviet Union, with an eye to subsequently running them as agents in their home countries
The Lubyanka Files. Here’s How the KGB Knew You’d Be a Traitor: an Exclusive Look at Its Recruitment Manual
The bottom line for spy recruitment comes down to this: look for the losers, especially the ones who want to think they are winners because they hang on to important positions.