Antivirus software from Avast blocked more than 34 million attempts to use computers for cryptomining last Sunday, the 3rd of December. Never before the antivirus vendor blocked so many attempts to abuse computers for cryptomining on a single day.
“Either this is a malicious campaign that was effectively spread, or a popular extension was modified to include the miner,” Konopiský writes.
In most cases this happens without the user noticing anything. However some users find out because the computer becomes slower because the mining script heavily utilizes the CPU.