If your phone is running slowly or always losing battery, it might have been hacked to mine cryptocurrency – here's how to protect yourself - Business Insider

A single smartphone doesn't have the necessary processing power to mine cryptocurrencies, but together, many devices can allow hackers to successfully do so. ....
https://www.businessinsider.com/cryptojackers-are-targeting-mobile-users-and-could-destroy-your-phone-2018-8