inetinfo.exe is used primarily for debugging Microsoft Windows Server Internet Information Services. This program is important for the stable and secure running of your computer and should not be terminated.
Any malware can be named anything - so you should check where the files of the running processes are located on your disk. If a "non-Microsoft" .exe file is located in the C:\Windows or C:\Windows\System32 folder, then there is a high risk for a virus, spyware, trojan or worm infection.
If your system is clean then high inetinfo.exe activity can be caused by IIS misconfiguration or probably some of your domains are overloaded by requests. Unfortunately Plesk can not control CPU load and level of IIS processes activity.
So this question is related to Microsoft products not the Plesk.
Please contact Microsoft in order to get more information.