Nowadays, systems that seemed to be least vulnerable to date are the real target of hackers. I’m talking about Linux. Over a year ago, ESET researchers found a plethora of OpenSSH backdoors, a weapon preferred by attackers that want to take control of servers. Researchers have found 21 families of malicious Linx-based software, including several undocumented. Operation Windigo brought together 25,000 servers, most of which based on Linux. The compromised machines were used to steal credentials, spam campaigns, redirect Internet traffic to malicious content, and other malicious activities.

https://www.welivesecurity.com/2020/02/20/linux-malware-should-you-worry/