Someone could be using your computer to mine cryptocurrencies without your knowledge. And this person may be located anywhere on the face of the earth.
Even if you use phones to browse the internet, most phones now are more powerful than an average PC, so it can be used for secret mining by some companies or individuals on their websites.
Recently the popular product for browser mining is coinhive. Websites register with it, get the scripts and mine on their visitors CPU. Coinhive gets 30% of the mining profit and gives 70% to the website owners. Coinhive only mines Monero as bitcoin can only be mined through an ASIC.
This trend has risen so high the past three months because of the rising price of crytocurrencies. However, there are plug-ins one can use to prevent illegal hijacking of CPU for mining.
Product like UNBLOCK ORIGIN, blocks mining scripts in your browser.
Recently companies like pirate bay, CBS’ showtime (a big media company) were caught with coinhive on their websites to mine crptocurrencies on their visitors’ CPU.