How to prevent users updating Notes in Salesforce?

To prevent users from updating Notes in Salesforce, develop a trigger on Note object and throw an error when someone tries to update the notes.
 
 
Sample Trigger:
trigger NoteTrigger on Note ( before update ) {
    
    for ( Note objNote : trigger.new ) {
        
        objNote.addError(
            'You cannot update the Note(s). Check with your Salesforce System Admin for assistance'
        );
        
    }

}
 
Output: