Your PC may be used to find cryptocurrency when you visit websites, with or without your consent. A report found that suggests hundreds of websites have taken The Pirate Bay's lead and are now using visitor PCs to mine cryptocurrency without the consent of users.

This autumn the news spread that some websites, including The Pirate Bay, had been making money by mining cryptocurrencies in their users? browsers. Security firm AdGuard looked for the codes for CoinHive and JSEcoin - the most popular solutions for browser mining in use now - on the Alexa list of the top one hundred thousand websites. The firm found that 220 sites that launch mining when a user opens their main page, with an aggregated audience of 500 million people. These people live all over the world; there are sites with users from the USA, China, South American and European countries, Russia, India, Iran? and the list goes on.

Cryptocurrency, such as Bitcoin or Monero can be "mined" and acquired through computational power. If enough PC owners donate power, then mining can be a way to rake in revenue.

In The Pirate Bay's case, the website's operators were experimenting with a mining script from CoinHive which hunted for Monero. The trial was explained as a potential way for the website to run for free, without needing to rely on adverts.

CoinHive and JSEcoin are currently the most popular scripts being employed to hunt down cryptocurrency, and Adguard estimates that these domains have earned roughly $43,000 in a three-week period at little or no cost.

Examining the website list more closely, AdGuard discovered that many of them are from the "gray zone", mostly pirate TV and video sites, Torrent trackers and porn websites.

The ethical way for a website to earn money by mining through its audience?s computers is to ask the audience for permission first, and to allow them the possibility to opt 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. Mining parasitizes the user?s CPU, where ads parasitize 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 of itself.

Adblockers will generally block the scripts that run in order to "hijack" your cpu.

Cloudflare recently started to suspend accounts and deny service to sites that mine without user permission.