The exponential growth in the price of cryptocurrencies has been accompanied by similar growth in email campaigns spreading cryptocurrency mining malware. There has also been a big rise in new mining malware variants, with three new malware variants detected in the past week. Conservative estimates suggest one malware variant has already been installed on at least 15 million systems, although the true figure could well be closer to 30 million.
The data comes from the cybersecurity firm Palo Alto Networks, which performed an analysis of the URLs used in the campaign using Bitly telemetry. It is difficult to determine how many systems have been affected since Bitly is not the only URL shortening service being used in the campaign. AdFly is also in use, which suggests the number of infected systems could well be twice as high.
The malicious links for this campaign are being sent in spam email. Clicking the links will direct the user to a malicious website containing executable files that install the Monero mining application XMRig using VBS scripts. The popularity of Monero mining is due to the lower processor demands than cryptocurrencies such as Bitcoin. Monero mining can take place on less powerful computers such as those typically at home. In addition to spam email campaigns, the malicious executable files are being loaded to popular file sharing websites
Cryptocurrency mining malware does not pose such a big threat to organizations as other forms of malware and ransomware, but there are implications for businesses. The malware does require a considerable amount of processing power, so there will be an impact on performance on infected machines. Infection will see applications slow considerably, and that will have an impact on productivity.
Campaigns are also being conducted that target businesses. The aim is to installing cryptocurrency mining malware on business servers. These attacks are not email-based, instead vulnerabilities are identified and exploited to install the malware, with Apache Struts (CVE-2017-5638) and DotNetNuke (CVE-2017-9822) vulnerabilities commonly exploited.
Preventing Infection with Cryptocurrency Mining Malware
Businesses can prevent cryptocurrency mining malware from being installed on their servers by ensuring all applications are patched and kept up to date. The patch to fix the Apache Struts vulnerability was released in September 2017, yet many businesses have not applied the patch. The DNN vulnerability has also been patched.
The risk of infections on employee and home computers requires antivirus and antimalware software and an advanced spam filter to prevent malicious messages from reaching inboxes. Businesses should also be training their staff how to recognize malicious emails. Training programs and phishing email simulations have been shown to help reduce susceptibility to email-based attacks by up to 95%.
The past few months have also seen a rise in cryptocurrency mining malware infections via unsecured WiFi networks, with cybercriminals performing man-in-the-middle attacks that hack the WiFi sessions of any user connected to one of the rogue WiFi access points. Unsecured public WiFi hotspots should be avoided, or VPNs used.