It's actually an interesting subjects of law and ethics. If you take advantage of someone's hardware without his knowledge, but at the same time you don't limit his abilities in any way, is it a crime?
I think it's usually a crime if you access someone's computer
without authorization.
In the US:
Many people whose computers were being used for mining didn't even notice and did not mine or plan to mine for themselves, so the hacker took advantage of their lack of knowledge and overall carelessness. He made money by using them, which is a bad thing, but he also did not make them lose money. Their computers were mining in the background only when these people were using them for other things, so they would be drawing power anyway at that given time whether they'd be infected or not.
How much does CoinHive, etc. slow down your computer? Maybe they "paid" by suffering through slower processing times.
They weren't accessing it. They added the virus to commonly downloaded programs, like the bones featured on freeware download sites and set the programs to connect to a pool with the hacker's login. Technically he was never accessing their computers.
I'm sure it slows them down significantly, but that's not the case. They were mining for weeks or even months without knowing it, so either they didn't notice or they did notice and didn't care.
