Russian security firm Dr. Web has discovered two new forms of a Linux Trojan: Linux.MulDrop.14 and Linux.ProxyM.1. The first one targets Raspberry Pi computers to mine cryptocurrency, while the second cloaks threat actors in anonymity.
Dr. Web first detected Linux.MulDrop.14 last month. It is composed of a bash script and a mining program. These scripts are designed to stop several running processes on the Raspberry Pi and install the libraries needed to operate. It also installs ZMap and SSHpass to search for other devices with open SSH ports.
When it finds another vulnerable device, the malware tries to spread itself using the Pi’s default credentials on SSH port 22. If it is able to get access, it unpacks and runs its payload.
An Odd Choice of Pi
The fact that this malware targets Raspberry Pi machines exclusively is somewhat unusual, since Trojans typically aim to infect as many different devices as possible. It’s also not ideal for cryptomining — while it does have some resources available to actually carry out the processes, they are less extensive than those found in most other modern computers.
A November 2016 update for the operating system in question disabled the SSH server by default, SecurityWeek explained. In other words, this ploy will only affect unpatched or older machines. Even so, Dr. Web advised users with SSH enabled to change their passwords as a preventative security measure.
Of course, upcoming versions of the Linux Trojan may cast a wider net.
The Proxy Linux Trojan
The other Trojan Dr. Web uncovered — Linux.Proxy.M — uses the special symbols of a terminal to confirm that it is not running in a honeypot. If it gets the all clear, it starts up a SOCKS proxy server. This proxy may hide the actor’s identity, as well as relay traffic and other network functions.
Dr. Web observed that 29 percent of attacked IP addresses were located in Russia — the largest portion out of any country recorded. The firm also reported that there have been 10,000 attacks since February 2017.
Even though Linux has fewer malware attacks than other systems, it doesn’t mean attacks are any less destructive when they do hit. Proper detection and security practices will aid in prevention and protection.