Cryptojacking is a process by which a computer or smartphone is hacked in order to remotely mine cryptocurrency without the owner’s knowledge. It uses a large amount of battery and can greatly slow down the device.
Opera, the web browser that has since December included anti-crypto mining in their integrated ad-blocker for desktop, announced that they will add this feature to their mobile browser as well.
Opera’s Vice President of Product Marketing Jan Standal described the process of cryptojacking during the company’s press release for their anti-mining software for mobile:
“When you browse the web, there are no visual clues that your device is exposed to mining. A single webpage you visit can take up to 4.5 hours of your battery time if you keep the tab open. This often turns out to be just the battery time you needed to use a ride-hailing app or check the map to get home.”
Websites in the past have admitted to using their visitors' devices to mine.
The Pirate Bay, in September 2017 admitted to using its user' CPU processing power to mine without their knowledge. Around the same time, Showtime was caught using its visitors' devices to mine, which they said was their way of getting around-ad blockers. Both these websites were mining for Monero through Coinhive which is a script that's advertised as an alternative to advertising.
https://cryptojackingtest.com/, use this site to see if your device has been affected by cryptojacking.
If you're interested in reading further about cryptojacking and the websites mentioned in the article, these links should help:
https://cointelegraph.com/news/how-to-check-if-your-pc-being-pirated-to-mine-bitcoin
https://cointelegraph.com/news/showtime-latest-secret-crypto-pirate-miner
https://cointelegraph.com/news/the-pirate-bay-is-pirating-your-processor-for-bitcoin-mining