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 >>/955332/
There is this thing called Proof-of-Work (PoW) that was invented to counter automated posting, bot activity. There are two types:
1. that needs user interaction to prove he is human
2. computational, that runs a script in the browser (thus proving a browser is open and the request is sent from it)
The first is captcha, although the second can be called that and there is a google captcha (and probably others) of the second type.
Since the second type needs computation it will use the CPU and depending on the complexity of the calculation (it generates a hash which is matched to another hash on the server when sent back) it can make the CPU (and the fan) go brrrr.
Perhaps it could be used to mine crypto with it, why not, if something needs to be calculated... I'm not aware of any real implementation of that, although I heard about Kohlcash I have not seen any proofs.