Forget viruses or spyware—your biggest cyberthreat is greedy currency miners

The practice of surreptitiously mining cryptocurrency on other people’s hardware is becoming pervasive, overtaking ransomware as a tool of choice for extorting money online.

This week, cybersecurity firm Check Point published its regular Global Threat Index. It shows that Coinhive, a piece of software that uses processing power on someone’s device in order to mine cryptocurrency, has become the most prevalent form of malware on the Internet. Another piece of cryptojacking malware, called Cryptoloot, is now the third most prevalent.

The rogue software exploits the way many cryptocurrencies are mined in order to turn a buck. Bitcoin and many of its newer rivals are given as rewards for performing the computationally demanding cryptographic operations that underpin the transaction records of the currencies—a process known as mining. Steal someone’s computing power by embedding such code in websites or software, and you can make money. Steal enough, and you can make a lot (see “Hijacking Computers to Mine Cryptocurrency Is All the Rage”).

“The problem,” explains Lotem Finkelstein, a threat intelligence analysis team leader at Check Point, “is that [cryptojacking is] simply everywhere—on websites, servers, PCs, and mobile.” Check Point says that it’s affected as many as 55 percent of organizations globally, while security researchers at Wandera claim instances on mobile devices increased by 287 percent between October and November of last year.

“It may be becoming a more serious issue than ransomware,” says Finkelstein, referring to attacks like last year’s WannaCry and NotPetya, which lock up computers in exchange for payment.

Other security experts agree. Speaking at a cybersecurity conference in Cambridge, UK, on Thursday, Max Heinemeyer, director of threat hunting at cybersecurity firm Darktrace, said that he has also observed the practice increase massively in recent months. On the sidelines of the event, he told MIT Technology Review that he, too, believes such attacks could overtake ransomware attacks as a global security threat.

That’s because it presents a better return on investment for hackers. Mining cryptocurrency is more likely to guarantee an income: ransomware attacks often go ignored, whether because a user knows they can back up their device, can’t afford the ransom, or doesn’t understand how to pay (ransoms are often payable in cryptocurrency, which many people aren’t familiar with using).

It also allows hackers to make money surreptitiously. Paul Ducklin of the security firm Sophos says that regular antivirus products should help many people identify and remove rogue mining software from their computers. But Heinemeyer explains that Darktrace—which uses artificial intelligence to spot unusual cyberthreats—has recently identified more sophisticated examples of cryptomining software installed on servers and websites that some rule-based threat detection tools wouldn’t spot.