I want to know more about this. Are they seeking any kind of consent from the users, or even disclosing it to the users? If not, I have serious doubts about the legality of this behavior.
It's worth noting that this isn't exactly a new idea - some MIT students had a project a couple of years ago that was basically that, except they tried to turn it into a startup. The viability of it was questionable back then as well.
https://en.wikipedia.org/wiki/Parasitic_computing
But it's a bit strange that the same broad concept can include subtle things where the indirect result of an activity is a computation that someone else wanted you to make, along with explicit cases where someone asks your device to run a full-fledged applet and it does so (to someone else's benefit).
I'd love to explore this idea in a more reasonable, less-sketchy, opt-in way, but I'm only just getting started with crypto and I'm not sure what factors go into estimating potential costs/returns yet.
(In the thread for the original Show HN for the code behind this: https://news.ycombinator.com/item?id=15246145 )
the only thing new is known organizations trying to do it for revenues.
In terms of specifics, maybe not anything criminal (though a prosecutor could try the CFAA), but on the civil side tort law trespass theories, maybe also unjust enrichment theories, would be well worth a try for a plaintiff's lawyer.
But really, I'm thinking in terms of more abstract legal ideas that could use some caselaw development to flesh out---the notion that there's an implied license to use resources on a user's computer to an ordinary extent and for an ordinary purpose---and grabbing onto those resources for this kind of extraordinary purposes without prior notice violates that license in just the same kind of way that (eg) triggering a more conventional malware download would. If you buy that theory (and I tentatively do), then there are lots of concrete legal doctrines to hook it to.
World of Warcraft and other games (apparently Windows 10 too) have used P2P (torrent-like) patch systems in the past, where after you downloaded a content update, you also distribute it to other users. AFAIK this was opt-out rather than opt-in. I think that falls under the same category of using the users' computer for an extraordinary purpose.