Here is an excellent site where you can search through a list of notable people who have resigned, been fired, or otherwise left high ranking positions. It is mostly USA-based but does include some notables worldwide.
You can search by name, by company, by position. Lots of options.
Remember that not ALL on the list are suspect. Obviously there is always some normal amount of turnover. But this list is a good place to start if you are investigating potential DS actors or compromised individuals.