The Kaspersky Lab Anti-Malware Research team has identified two crypto-mining botnets comprising thousands of infected PCs.
When a device is infected with crypto-mining malware, the graphics card or processor of the infected device is used to secretly mine and send cryptocurrency to the attacker.
The researchers estimated that a 4,000-machine network could bring its owners up to $30,000 a month, and witnessed criminals scoring more than $200,000 from a 5,000-PC botnet in one instance.
Bitcoin is not very profitable to mine using a standard PC, and cybercriminals are directing their botnets to mine digital currencies like Monero and ZCash.
These altcoins have seen a large increase in value this year and have the advantage of providing users with anonymity.
Kaspersky’s research showed a steady increase in cryptocurrency miner-related malware over the last few years, with the number of threats blocked growing from 701,000 in 2014 to 1.65 million in the first 8 months of 2017.
The company warned that this malware is commonly installed within adware, and advised consumers to avoid suspicious downloads and update their security solutions.