Researchers have discovered that criminals are surreptitiously mining cryptocurrencies directly in unsuspecting victims' web browsers.
Criminals choose sites that can mask higher than normal computer processor load caused by the mining scripts, ESET said.
Russia and the Ukraine had the highest instances of malicious mining, according to the security firm.
Mining Bitcoin via web browsers was the legitimate business of a company name Tidbit, which was sued by the New Jersey attorney-general for using people's computing power without permission. Tidbit folded after reaching a settlement with the New Jersey authorities.