It's not really a big surprise, but in a new report, Microsoft singles out coin mining malware as a growing threat. Due to the increased value of cryptocurrency coins, more and more cybercriminals are using malware campaigns to install and run miners on other people's computers.
Cybercriminals repackage or modify existing miners and then use social engineering, dropper malware, or exploits to distribute and install the trojanized cryptocurrency miners on target computers. Every month from September 2017 to January 2018, an average of 644,000 unique computers encountered coin mining malware.
Full details at Microsoft Secure. Besides coin mining malware, there's also a growing incidence of websites that use coin mining scripts to earn money. In some cases, these pages may have been hacked by cybercriminals.