masalert.exe is part of McAfee Anti Spyware and its function is to alert the user of any spyware. You should leave the process running if you intend to use McAfee Anti Spyware.
Non-system processes like masalert.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