ESET researchers discovered Kobalos, a malware that has been attacking supercomputers and servers. The malware is portable to Linux, BSD, Solaris, and possibly AIX and Windows. It grants remote access to the file system, provides the ability to spawn terminal sessions, and allows proxying connections to other KobalOS-infected servers. In addition, in most systems compromised, the client for secure communication (SSH) is compromised to steal credentials. The use of stolen credentials seems to be one of the ways it is able to propagate to different systems.
Source: https://www.helpnetsecurity.com/2021/02/02/linux-malware-backdoors-supercomputers/