Disabling Norton Antivirus Performance Alerts. 1. Open NAV main window, click on Settings. 2. Click General tab, in the left pane, click on Performance Monitoring and set ‘Performance Alerting’ switch to ‘Off’ position.3. Click ‘OK’ to apply the changes.imilarly, Norton Antivirus monitors the system performance and offers Performance Alerts, which are enabled by default. If any program or process consumes too many system resources, then you’ll be notified with a notification with the message ‘high disk usage by..