Linux users (those who run a Linux instance on their personal PC) are all “server administrators”.
And there are piles of free apps/utilities out there, more than one could be compromised.
And, to top it off, Linux users rarely install anti-malware systems, so the scale of infection is unknown.
These are Network Servers, not personal machines being referred to in the article.
First sentence in the article: “For over 5 years, and perhaps even longer, servers around the world running Linux and BSD operating systems have been targeted by an individual or group that compromised them via a backdoor Trojan, then made them send out spam, ESET researchers have found.”
Also first sentence in the thread.
Just FYI.
The article says these are mostly web servers, probably located in data centers. Home users would not be interested in a pirate copy of the type of software offered by this company.
However, it is true that there are many slovenly individuals who rent servers in data centers. You can get a virtual root-server for $14.99 a month nowadays.