PUA not detected - hides itself while scanning

HI,

on one of our server is a  PUA running, no matter what we tried (online scan / offline scan) it is not detected. The PUA uses some kind of stealth mode. When you try to execute scan on an affected file you can see that the mousepointer moves away from the selected file. Off course, we can clean the server with fresh install, my intent is to be able to detect such software.

What is the recommended way to proceed ?

regards