A cryptocurrency mining code called Coinhive is creeping onto unsuspecting websites around the net.
So, when you visit a website with Coinhive code your computer is working to mine cryptocurrency for someone.
Coinhive itself is not Malware.
Coinhive is not malware by itself. Coihive code is a technique to generate income from websites as an alternative to running ads on the site. When the user is notified up front and is given the choice to leave the site or continue then we have no moral objection.
However, often the code is not disclosed to the user.
Even worse, hackers are now installing the code on unsuspecting websites in order to profit. Most of the victims are using an older version of Drupal that has vulnerabilities that can be exploited to install the script.
Mining the cryptocurrency Monero is the most common use for the Coinhive mining code. In fact, the folks that run Monero are aware of this issue and working on solutions to lesson the attacks.