The easiest way is to disallow "GoogleUpdate.exe" to access Internet using your system Firewall. You can create a new rule for it.
If you don't use a firewall or don't want to use the first method, then you can use following steps to permanently remove the "GoogleUpdate.exe" file from your system but remember that after removing the file you'll no longer be able to update the Chrome web browser using its built-in update function. You'll need to manually download the new version.
1) First disable "GoogleUpdate.exe" from system startup. Type msconfig in RUN dialog box and press Enter. It'll open "System Configuration" window. Now goto "Startup" tab and uncheck "GoogleUpdate" from the list.
Apply the changes and restart your system.
PS: You can also use Registry Editor or any other 3rd party utility to remove startup entry. Windows Defender can also do the job.
2) Now we'll need to remove the scheduled task created for GoogleUpdate.exe from our system. Open "Scheduled Tasks" or "Task Scheduler" from Control Panel or Programs menu. You can also run it by directly providing "taskschd.msc" command in RUN dialog box or by opening "%windir%\Tasks" folder.
Now look for the "GoogleUpdateTaskUser" task and delete it.
You can also disable the task instead of deleting it.
3) Now the last thing. We'll need to remove the "GoogleUpdate.exe" file permanently so that it doesn't add its entry in startup.
Go to the following folder:
C:\Documents and Settings\Administrator\Local Settings\Application Data\Google\Update
Replace C: with your system drive where Windows is installed and replace "Administrator" with your user name in Windows.
In the above folder, you'll find the "GoogleUpdate.exe" file. Delete the file.
If you find any difficulties in deleting the file, then make sure GoogleUpdate.exe is not running in background, if its running then End Task of it using Task Manager and then try to delete it again.
4) That's it. Now you'll no longer see "GoogleUpdate.exe" file in background process list.
You can also download and install the Offline installer of Google Chrome which doesn't include the "GoogleUpdate.exe" file:
Chrome Offline Installer: Full Standalone Installer Without Google Update
Or you can use the Portable version of Google Chrome which doesn't need to be installed:
Download Portable Version of Google Chrome, No Need to Install
Source: How to Remove Annoying GoogleUpdate.exe Background Process After Installing Google Chrome?