I think I know the cause but maybe not

[Jude DaShiell]

There are times when I want to use my zip drive with /dev/sda4 and shortly 
after a linux installation is done and the system goes online this is 
possible.  However repeatedly about a week after system goes online, I 
find all /dev/sd* devices missing and this was with the automatic yum 
update facility turned on.  I suspect either malware or root compromise. 
Is one of these the most likely cause or is there something else I don't 
yet know about.  No, I don't go around moving editing or deleting anything 
in the /dev/ directory either.