The BBC has reported that a number of websites, including those that belong to the government, were hijacked to include software that mined digital currency in the background. 

The upshot of this is that criminal gangs can use legitimate services such as Coinhive to generate cash.

Fortunately organisations (or members of the general public) can use simple tools such as LogRhythm's Network Monitor Tool (freemium version available) to look for network connections made by browsers in the background to sites such as CoinHive.