One of the latest developments in cybersecurity is the advent of microstealing. Criminals are planting software that uses your computer hardware to accomplish tasks.
The criminals may add software to a site, so when you read the news, a script runs in the background that mines cryptocurrency. The criminals earn a little money from each person who visits the site.
It does affect the person who they use the computing power from, since the computer uses more electricity and may perform other operations slower than normal.