netmon.exe is a process which is registered mass-mailing worm. "This virus is distributed via the Internet through e-mail and comes in the form of an e-mail message, in the hopes that you open its hostile attachment. " The worm has it's own SMTP mailing engine which means it gathers E-mails from your local computer and re-distributes itself. "In worst cases this worm can allow attackers to access your computer, stealing passwords and personal data. " This process is a security risk and should be removed from your system.
Non-system processes like netmon.exe originate from software you installed on your system. Since most applications store data on your hard disk and in your system's registry, it is likely that your computer has suffered fragmentation and accumulated invalid entries which can affect your PC's performance.

In Windows Task Manager, you can see what CPU, memory, disk and network utilization is causing the Trojan.W32.MIMAIL process. To access the Task Manager, hold down the Ctrl + Shift + Esc keys at the same time. These three buttons are located on the far left of your keyboard.

Warning! netmon.exe is considered to be a dangerous process and should be removed. Running issues with this process can increase the risk of malware infection if bugs are present. Scan your system with an anti-malware software to identify unused processes and services that can be safely removed. The netmon.exe was found in the folder C:\Program Files\Network Monitor.

This process is not considered CPU intensive. However, running too many processes on your system may affect your PC’s performance. To reduce system overload, you can use the Microsoft System Configuration Utility (MSConfig) or the Windows Task Manager to manually find and disable processes that launch upon start-up.

Use the Windows Resource Monitor to find out which processes and applications write/read the most on the hard drive, send the most data to the Internet, or use the most memory. To access the Resource Monitor, press the key combination Windows key + R and then enter 'resmon'.