Ad blocking firm AdGuard has found that over 500 million people are inadvertently mining cryptocurrencies through their computers after visiting websites that are running background mining software. The company found 220 popular websites with an aggregated audience of half a billion people use so-called crypto-mining scripts when a user opens their main page. Newsweek reports: The mining tool works by hijacking a computer’s central processing unit (CPU), commonly referred to as “the brains” of a computer. Using part of a computer’s CPU to mine bitcoin effects the machine’s overall performance and will slow it down by using up processing power. The researchers found that bitcoin browser mining is mostly found on websites “with a shady reputation” due to the trouble such sites have with earning revenue through advertising. However, in the future it could become a legitimate and ethical way of making money if the website requests the permission of the visitor first. “220 sites may not seem like a lot, ” the researchers wrote in a blogpost detailing their discovery. “But CoinHive was launched less than one month ago on September 14. The growth has been extremely rapid: from nearly zero to 2.2 percent of Alexa’s top 100, 000 websites. “This analysis well illustrates the whole web, so it’s safe to say that one of every forty websites currently mines cryptocurrency (namely Monero) in the browsers their users employ.” Read more of this story at Slashdot.