Killing C.I.A. Informants, China Crippled U.S. Spying Operations
From my readings of CIA memoirs and spy novels, CIA Agents (aka sources or informants) are really foreign people reporting information to the CIA Officers which are US Government employees.If these were US government workers reporting secrets to the Chinese I would expect imprisonment, etc. I guess it isn't too shocking they would do the same, albeit more cruelly, to their own traitors.There was a post recently about how easy it was for foreign governments, in the 1970's, to track the actual CIA Officers on station at an embassy.  TL;DR:  Reading job titles and observing who they hung out with was one way.  Also mentioned was that CIA officers rarely intermingled with actual Diplomats and support staff often knew who was who because of secret areas of the embassy that were off limits.The article mentions a potential hack into the systems but it could have been good old spy-craft by following people and noticing patterns to find the sources.