As extensive computing power is required to harvest cryptocurrency using complex algorithms, a recent malware trend has been to link computers visiting a website into the process.  While most of the malware agents have likely been removed, users must remain careful at all times while online.

https://www.androidheadlines.com/2018/01/cryptocurrency-mining-ads-sighted-on-youtube-report.html

Video giant YouTube is the latest site to be hit with reports of advertisements that secretly utilize unwitting users’ computing power to mine cryptocurrency. According to a number of scattered international reports gathered by Ars Technica from Japan, France, Taiwan, Spain, and Italy, antivirus programs are finding cryptocurrency mining code running on users’ computers when they go to YouTube. Most of the mining ads in question seem to be mining a type of cryptocurrency called Monero and are JavaScript-based, allowing them to do their work through a seemingly normal ad on any web page. YouTube, for its part, has yet to put out any sort of official statement about this phenomenon. Most of the information about the ads was gleaned by security analyst firm TrendMicro, as well as various antivirus programs such as Avast.