An analysis of more than 4.4 million malware samples showed botnets were responsible for crypto-mining at least 4.3 percent of Monero over a 12-year period.

These illicit efforts generated an estimated $56 million for cybercriminals behind the campaigns. The study from academics in the U.K. and Spain used a combination of both dynamic and static analysis techniques to pull details from the malware campaigns, including an exploration of the mining pools where payments were made as well as cryptocurrency addresses. Over the 12 years, Monero (XMR) was the most popular cryptocurrency targeted by botnets, the study concluded.

New Crypto-Mining Threat Groups Discovered

While the research paper mentioned previously known malware campaigns such as Smominru and Adylkuzz, the study’s authors also noted some new threat actors. These included Freebuf and USA-138, which used general-purpose botnets rather than renting third-party infrastructure to carry out their mining operations.

Though the latter technique tended to be more successful based on the analyses in the study, the findings are a reminder that cybercriminals are highly capable of using legitimate file management tools and code repositories for illicit purposes.

Since mining pools are known to ban suspicious XMR addresses from time to time, and because mining protocols are subject to change, the researchers concluded that some malware authors often modified their code. Some of these campaigns are still active, while others were relatively brief, according to the paper.

In terms of methodology, the researchers said xmrig, an open-source tool, was most commonly used to build the malware strains that powered crypto-mining bots.

Catching Crypto-Mining Before It Happens

Beyond the money it generates for threat actors, crypto-mining, also known as crypto-jacking, has the secondary adverse impact of draining an organization’s central processing unit (CPU) resources.

IBM X-Force research published last year confirmed that crypto-mining has grown significantly over the past few years and needs to become an active part of IT security monitoring. As it becomes a more persistent threat, utilizing security information and event management (SIEM) tools combined with strong endpoint protection is one of the best ways to ensure your technology infrastructure doesn’t become a place for criminals to harvest Monero.