mrtstub.exe is a process belonging to an unclassified malware which can download other malicious processes and cause unwanted behavior on your computer. This process should be terminated immediately.
Non-system processes like mrtstub.exe originate from software you installed on your system. Since most applications store data in your system's registry, it is likely that your registry has suffered fragmentation and accumulated invalid entries which can affect your PC's performance. It is recommended that you check your registry to identify slowdown issues