The list of these sites primarily consisted of porn sites and torrent trackers.
"220 sites may not seem like a lot. But CoinHive was launched less than one month ago, on the 14th of September," AdGuard said. "The problem with in-browser mining is not that it's a bad thing by itself. There are no good and bad tools and technologies, but there are good and bad ways to use them."
The ad blocker firm said a website seeking to generate revenue via mining should ethically obtain user permission and allow them the option of opting out.
"Actually, such a practice could make mining even more ethical than ads. After all, nobody asks us if we would like to see ads on a website," AdGuard said. "Mining parasitises the user's CPU, where ads parasitise the user's attention, emotions, bandwidth, and often, their laptop or smartphone battery, and supports an industry of personal data harvesting that is a big headache in itself.
"The CoinHive team has issued a statement calling on website operators to inform their users about the mining operations and to ask for user permission to do this. However, we believe that it is very hard for them to force this recommendation into action; for example, they cannot forbid stealth mining."