However, you can monitor the CPU usage when your computer is idle, then, any an usual activity such as a high CPU usage should be considered as a suspect activity.
Am not familiar with Docker and how it works, so is this affecting linux users only?
Yeah, I agree that it really depends on the program that you are running, but if you are just browsing and not doing heavy stuff specially if you have a dedicated machine setup just for your crypto, it shouldn't be as high as 50% perhaps.
I've almost monitor the health of my machine, specially when I log on here in bitcointalk and see if there are some "abnormal' CPU fluctuations. There are browser extensions that supposedly to block crypto jacking, but I haven't check them out though.