The big question would be how you manage to install this on servers? Remember, there are no dumb users who will click on a link in an email, it’s a Linux server! Without root access, no malware could be installed.
The following paragraphs are interesting:
“The price of the software is $240, but interestingly enough, there is a link to a site offering a “cracked” version of DirectMailer. The developers explicitly say that they don’t provide technical support for users of pirated versions of DirectMailer downloaded from that site or any other, but the fact that they provide a direct link is strange.”
“The pirated DirectMailer copies contain the Mumblehard backdoor, and when users install them, they give the operators a backdoor to their servers, and allow them to send spam from and proxy traffic through them.”
So in order to get infected, you would have to download the ‘pirated version’, log in as root, and install it. This is a deliberate act by a server administrator who knows he is doing something illegal and risky. I guess end users aren’t the only dumb ones out there.
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.