I have a former coworker who was the VP of Finance at my company. He suddenly got fired out of the blue. The company was in the midst of trying to find a buyer (this was announced) so this was extra surprising. Turns out, he knew a lot of bad news about the company, and they caught him looking for a job. They fired him because he was too much of a liability.
How did they catch him? He was putting resumes and cover letters on OneDrive. "Yeah, in retrospect, that's one of the dumber things I've ever done," he said to me later.