Symptoms of in-browser Mining
The problem with in-browser mining services like CoinHive is that in most cases a user has no idea that their browser is being used for this purpose. They may find that their computer starts to act slow, but there is no outward indication that anything is wrong.
The only way they would be able to tell that something is not right is if they looked in the Windows task manager and noticed that the browser process was utilizing a lot of CPU. For example, in the image below we see chrome.exe utilizing 97% of the CPU.